BORDEN, J.

This certified habeas corpus appeal raises two principal issues. They are: (1) whether habeas corpus recognizes a claim of actual innocence affecting the fairness of the petitioner's criminal trial even if that claim does not depend upon an antecedent constitutional violation; and (2) whether, in the circumstances of this case, the petitioner has produced sufficient evidence to require a remand to the habeas court for a consideration of his claim of actual innocence because his conviction of manslaughter in the first degree in violation of General Statutes 53a-55(a)(1) had been based on unreliable medical evidence.

Pursuant to our grants of certification to appeal, the petitioner, Robert Summerville, appealed, and the respondent, the warden of the state correctional institution at Somers, cross appealed from the judgment of the Appellate Court. That judgment: (1) affirmed the determination of the habeas court that the petitioner had not been denied his constitutional right to the effective assistance of counsel at his trial; and (2) reversed the judgment of the habeas court insofar as that court had not evaluated the evidence produced by the petitioner purporting to establish that his original conviction had been based on unreliable medical evidence. See Summerville v. Warden, 29 Conn. App. 162, 614 A.2d 842 (1992). With respect to the reversal, the Appellate Court remanded the case to the habeas court for a determination of the merits of the petitioner's claim.

We granted the petitioner's petition for certification to appeal, limited to the following issue: "Did the Appellate Court correctly conclude that it should not decide the issue of whether an ineffective investigation by a defense expert witness in a fashion that impairs the petitioner's defense is impugned to the defense attorney?" Summerville v. Warden, 224 Conn. 918, 617 A.2d 172 (1992). We also granted the respondent's petition to appeal, limited to the following issue: "Did the Appellate Court have proper grounds for remanding this case to the habeas court for a consideration of expert testimony that was not presented at the petitioner's criminal trial?" Id.

We conclude that the petitioner's petition for certification was improvidently granted, and we therefore decline to consider the issue presented by that petition. With respect to the issue presented by the respondent's petition for certification, we agree with the Appellate Court that a claim of actual innocence of the crime of which the petitioner has been convicted is cognizable in a habeas corpus proceeding. We conclude, however, that the evidence produced by the petitioner in this case was insufficient to establish such a claim on habeas corpus, and was, therefore, insufficient to justify any remand to the habeas court for evaluation of that evidence. Accordingly, we reverse the judgment of the Appellate Court.

I

A proper understanding of our determination of the issues presented in this case requires a thorough review of the evidence produced at the petitioner's criminal trial and at the habeas proceeding, as well as the procedural history of this case. The evidence supporting the petitioner's conviction was summarized in his original appeal on the merits in the Appellate Court. "On October 12, 198[4], the [petitioner] and the victim, who had been friends for several years, met in a bar in Bridgeport. The victim invited the [petitioner] to attend a party in Stamford later that evening. Instead of attending the party, the two checked into a hotel room in Stamford at approximately 11:30 p.m. that evening. Both the victim and the [petitioner] remained in the room for several hours drinking, socializing, and ingesting cocaine.

"At approximately 5:30 a.m. the following morning, the [petitioner] summoned a security guard to the room claiming that the victim had suffered a stroke. When the security guard entered the room, he observed the victim on the floor partially covered by a bed sheet. He checked for a pulse but found none. The security guard called the police for assistance. Terrance Shea, a Stamford fireman and emergency medical technician, responded to the scene shortly thereafter. Shea checked the victim's pulse and upon finding none began efforts to resuscitate the victim. Resuscitation efforts continued until the victim arrived at Stamford Hospital, but the victim never responded and was pronounced dead.

"At trial, the state produced Arkady Katsnelson, an associate chief medical examiner, who testified that the victim died as a result of manual strangulation. Katsnelson further testified that he found an abrasion on the victim's neck below the left ear which seemed to have been caused by someone's fingernail. Katsnelson also noted a separation of the victim's hyoid bone, a U-shaped bone deep inside of the neck, hemorrhages to the victim's neck, eye, heart, and lungs, and cocaine in the victim's blood and nose.

"The [petitioner] called Elliot Gross, the former chief medical examiner in Connecticut, to support his theory that the victim died of cocaine intoxication. Gross, after reviewing the records and examining the larynx, tongue and hyoid bone which were made available to him through the chief medical examiner's office, testified that the victim's injuries and hemorrhages were due to the resuscitation efforts. On cross-examination, Gross conceded that microscopic slides of the areas of hemorrhaging could determine if the injuries had occurred before or after death, but that he did not order such slides in this case.

"The state then called William Q. Sturner, chief medical examiner for the state of Rhode Island, as a rebuttal witness. Sturner rebutted Gross' opinion by testifying that the injuries he observed were inconsistent with resuscitation. He based his testimony in large part on his examination of microscopic slides made from the area of hemorrhaging, the type of slides the [petitioner's] expert chose not to order. By examining the microscopic slides of where the hemorrhaging occurred, Sturner was able to determine that the hemorrhages occurred before the victim stopped breathing, and therefore were not the result of resuscitation efforts. Sturner concluded that the death of the victim was by strangulation." State v. Summerville, 13 Conn. App. 175, 176-78, 535 A.2d 818 (1988).

In addition to this evidence, the following evidence was presented to the jury at the petitioner's criminal trial. Thomas Aiello, the occupant of the adjoining hotel room, testified that shortly after 5 a.m. he had heard heavy breathing, grunting and slapping noises coming from the petitioner's room, and that he had heard a woman's voice say "stop." Aiello interpreted the sounds as those of vigorous sexual activity, but the autopsy indicated no signs of recent sexual activity, and the petitioner did not describe any sexual activity with the victim in his statements to the police.

Gregory Cinque, a hotel employee who had assisted in the attempts to resuscitate the victim, testified that the victim's tongue had been protruding from her mouth. In addition, there was evidence that the bedclothes had been bloodstained, and that there had been blood under the victim's fingernails.

There was also evidence that the petitioner had summoned Irwin Osorio, the hotel security guard, to the room. He told Osorio that the victim had suffered a stroke while he and the victim had been fighting, and that he had tried to put her protruding tongue back into her mouth. The petitioner later told the police that, as the victim had gotten up from the bed to go to the bathroom, she had experienced a seizure and had fallen to the floor. He also stated to the police that the victim had choked on her tongue, and that when he had forced her jaw open and reached into her mouth to pull her tongue out, she had bitten his hands. The police observed marks or scratches on the backs of the petitioner's hands and fingers, but the physician who treated him at the hospital emergency room observed no wounds on his palms.

Katsnelson performed the autopsy on the victim. His initial external examination of the body disclosed certain marks and hemorrhages that he recognized as signs of asphyxiation, namely, a crescent-shaped abrasion on the left side of the victim's neck, that he attributed to pressure from a fingernail, and antemortem petechial hemorrhages in the victim's lower left eyelid.

In addition, Katsnelson's autopsy disclosed other indications of asphyxiation. There were petechial hemorrhages in the posterior aspect of the heart and in the posterior and lateral aspect of the lung. There were also antemortem hemorrhages on the left sternocleidomastoid muscle and the left sternohyoid muscle, located in the area where the neck connects to the collarbone.

Further, according to Katsnelson, the victim's hyoid bone, which is a horseshoe shaped bone located deep in the upper part of the neck, had a separation of its right horn with hemorrhages in the connecting soft tissue. Katsnelson testified that during the autopsy he had performed the extraction of the hyoid bone with particular care so as to avoid any artifactual damage to it because, from his external observations of the victim's body, he had suspected manual strangulation as the cause of death. He testified that he had observed the separation before removing the bone from the soft tissue in the victim's neck. He also testified that, although he had nicked the left horn of the bone with his scalpel during the removal process, the separation of the right horn of the bone and the associated tissue hemorrhages were not artifactual. Katsnelson also testified that, in his opinion, the separation that he had observed in the right horn of the hyoid bone, and the hemorrhages that he had observed on the sternocleidomastoid and sternohyoid muscle on the victim's left side, indicated pressure from manual strangulation on both sides of the victim's neck. Katsnelson also testified that the victim's epiglottis area, including the vocal box, the vocal chords and the base of the tongue, had been swollen and had dark red hemorrhages. He could not exclude intubation, which is the insertion of a tube down the victim's throat, during resuscitation efforts as the cause of these findings.

Katsnelson testified further that, although the body had no external injuries ordinarily associated with manual strangulation, other than the crescent-shaped mark on the left side of the neck, "it is possible to strangle a person without evidence of [external] injuries." Moreover, although the victim had a blood level of cocaine of 2.63 milligrams per liter, in Katsnelson's opinion that was not necessarily a fatal level, particularly because she had inhaled, rather than injected, the cocaine and, in his experience, fatal inhalation of cocaine usually evinces a blood level of nearly 4 milligrams per liter. Thus, Katsnelson concluded, that on the basis of his performance of the autopsy, which included his personal examination of all pertinent parts of the victim's body, the cause of the victim's death was asphyxiation resulting from manual strangulation, and not cocaine intoxication.

Gross, who had been the chief medical examiner for the state of Connecticut and was at the time of trial the chief medical examiner for the city of New York, had examined the petitioner's statement, Katsnelson's autopsy report, certain photographs that had been taken during the autopsy, parts of the victim's neck area, namely, her tongue, larynx, thyroid cartilage and hyoid bone, and certain wet tissue specimens from that area. On the basis of his examination of those photographs, he was of the opinion that the crescent-shaped mark on the left side of the victim's neck had been caused by a mask having been placed over her face during resuscitation efforts. He also conceded, however, that the mark was consistent with manual strangulation. It was also his opinion, based on his examination of the photographs, that the hemorrhages in the victim's eyes were not petechial, that the hemorrhages in the left sternocleidomastoid muscle and left sternohyoid muscle had been caused by intubation during resuscitation efforts, and that hemorrhages on the surface of the victim's heart muscle were consistent with a cocaine-induced convulsion, as the petitioner had described in his statement. Gross also opined, based on his examination of the hyoid bone, that the separation in the right horn of the bone was artifactual, having been caused by Katsnelson during the autopsy. It was also Gross' opinion, based on his examination of the tissues, that the hemorrhages in the epiglottis area were not petechial, and had been caused by intubation.

Gross further testified that one would expect to find significant external injuries on the victim's body following manual strangulation, but that they do not always occur in such a case. He also testified that he had not prepared or examined any microscopic slides of the victim's tissues, and that, if injuries had occurred within one hour of death, such slides would not have conclusively shown whether the injuries occurred before or after death. Gross testified further that, in his opinion, the cause of death was acute cocaine intoxication.

Sturner had examined Katsnelson's autopsy report, Gross' report of his findings, the hospital report of resuscitation efforts, including summaries of interviews with emergency room personnel, the report of the emergency medical personnel who had been summoned to the hotel, autopsy photographs of the victim's body, the wet tissue specimens of the victim's laryngeal area, the victim's hyoid bone itself, the arrest warrant affidavit, and the transcript of the probable cause hearing. He also prepared and examined microscopic slides of four areas: the hyoid bone separation; the right epiglottis; the left epiglottis; and the left upper trachea. He testified that the purposes of such slides were to confirm findings made by visual examination, and to disclose any new information bearing on the question of whether certain injuries had been inflicted before or after death.

On the basis of the autopsy photographs, Sturner testified that, in his opinion: the crescent-shaped mark had been inflicted by a fingernail antemortem; the hemorrhages in the left eyelid were petechial; and the hemorrhages on the left sternocleidomastoid muscle and the left sternohyoid muscle had not been caused by intubation or resuscitation efforts. With regard to the hyoid bone separation, Sturner could not give an opinion as to whether the separation was artifactual; he could not tell from his visual examination of the bone itself, and his microscopic slides neither confirmed nor ruled out either possibility.

On the basis of the slides, however, Sturner was able to give his opinion regarding the hemorrhages in the epiglottis area and the trachea. He testified that he found, by visual examination, hemorrhages on the epiglottis areas, and that the microscopic slides confirmed his opinion that these hemorrhages were on both sides, had been caused before death, and had not been caused by intubation. Similarly, he testified that, on the basis of his visual examination, which was confirmed by the slides, the hemorrhages on the trachea were petechial, had been caused before death by asphyxia, and had not been caused by intubation. Relying on his observations, Sturner testified further that, in his opinion, the cause of death had not been cocaine intoxication.

All three forensic pathologists agreed that, in a given case, different pathologists could view the same data and reach different conclusions about the cause of death. That much is apparent from their testimonies. Thus, the differences in their opinions resulted from differing interpretations of the same data.

The petitioner's criminal trial concluded with the judgment of conviction rendered on December 5, 1985. The Appellate Court affirmed the judgment of conviction on January 5, 1988. See State v. Summerville, supra, 13 Conn. App. 175.

II

The petitioner brought this habeas corpus action by way of a petition, in two counts, filed on September 14, 1990. In the first count, the petitioner alleged that he had been deprived of his rights to due process of law, under the fourteenth amendment to the United States constitution and article first, 8, of the Connecticut constitution, because the medical evidence that had been presented to the jury "was unreliable as indicia of manual strangulation." Specifically, he alleged that the evidence was "medically unreliable" because the hemorrhage in the victim's left eyelid was not petechial, the petechial hemorrhages on the heart surface were consistent with cardiopulmonary resuscitation performed on the victim, the hemorrhage of the sternocleidomastoid muscle was not petechial, the hemorrhages to the laryngeal area were not petechial, and the crescent-shaped abrasion on the victim's neck was "at the jawline."

In the second count, the petitioner alleged ineffective assistance of his trial counsel, under the sixth and fourteenth amendments to the United States constitution and article first, 8, of the Connecticut constitution. Specifically, he alleged that his trial counsel had failed: to request a continuance, or to accept the state's offer of a continuance, for Gross to examine Sturner's microscopic slides; to research the difference between the manners of development of petechial and nonpetechial hemorrhages; and to present surrebuttal evidence that the laryngeal hemorrhage was not petechial.

During the habeas trial, the habeas court permitted the petitioner to amend his petition further in order to conform to his proof. His third amended petition, filed in court on January 31, 1991, differed from the second amended petition only with respect to the allegations in the first count that the medical evidence at trial had been medically unreliable. Whereas in the second amended petition he had alleged that "[t]he hemorrhages to the laryngeal area were not petechial," in this third amended petition he alleged that "[t]he hemorrhages to the laryngeal area were more consistent with attempts to resuscitate the victim by intubation than with manual strangulation." The allegations of the second count, regarding the petitioner's ineffective assistance of counsel claim, remained the same.

At the habeas hearing, the evidence pertinent to the petitioner's claim, on the first count, that the evidence of the victim's death was medically unreliable consisted of the testimony of Katsnelson and of Mark Taff, a forensic pathologist. Katsnelson was called by the petitioner for the purpose of introducing into evidence certain records, including the hospital report of death, the toxicology report, Katsnelson's autopsy report, and Sturner's slides. Thereafter, in response to questions by the habeas court, Katsnelson testified that it was not a usual and necessary part of ordinary autopsy protocol to prepare microscopic slides. He testified further that such slides are prepared only if the medical examiner decides that they are needed, and that, in this case, although he had been informed about the resuscitation efforts on the victim, the injuries he had observed were not consistent with such efforts.

At the time of the petitioner's criminal trial, Taff had been the deputy medical examiner for the Nassau County Medical Examiner's Office in New York. Taff had reviewed Katsnelson's autopsy report, the toxicology reports regarding the level of cocaine in the victim's blood, the autopsy photographs, the microscopic slides prepared by Sturner, and reports of the Stamford police department, hospital reports, and summaries of interviews with hospital personnel. Thus, he had not examined any of the actual body parts of the victim, including the hyoid bone, or the wet tissue specimens of her epiglottis area, which were no longer available when he was employed by the petitioner for these proceedings. He also had not reviewed the trial testimony of Aiello, Cinque or Osorio.

Taff testified that it was his opinion, based on the materials that he had reviewed, that the crescent-shaped mark on the victim's neck was not a significant finding and that the mark was attributable to someone having handled the victim's head or to the victim having scratched herself. Regarding the hemorrhages in the victim's left eyelid, it was Taff's opinion that they were confluent, not petechial, hemorrhages, and that they had been caused by the victim having fallen and hit the left side of her head. He testified further in this regard that, had there been manual strangulation, he would have expected to see right eyelid hemorrhaging as well. Taff agreed with Katsnelson's opinion that there were petechial hemorrhages on the posterior aspect of the victim's heart and on the posterior and lateral aspects of her lungs, but Taff attributed these hemorrhages to cardiopulmonary resuscitation. Regarding the hemorrhages on the victim's left sternocleidomastoid muscle and left sternohyoid muscle, it was Taff's opinion that these hemorrhages had been caused by Katsnelson's having nicked the victim's jugular vein during the autopsy, and that these hemorrhages were not what one would expect to see as a result of manual strangulation. Taff also testified that it was his opinion that the separation of the hyoid bone was artifactual, having been caused during its removal by Katsnelson during the autopsy. Regarding the epiglottis area, Taff testified that there were small focal hemorrhages and small areas of petechial hemorrhages on both the right and left sides of the vocal chords. It was his testimony that these had been caused by intubation and other efforts at resuscitation.

Furthermore, Taff considered it significant that there were no external injuries indicating manual strangulation. Considering the toxic blood level of cocaine, the petitioner's statement that the victim had suffered a seizure, and the lack of findings consistent with manual strangulation, Taff opined that the cause of the victim's death had been acute cocaine intoxication.

The evidence pertinent to the petitioner's claim, on the second count, of ineffective assistance of counsel consisted of the testimony of Stephen F. Donahue, the petitioner's trial counsel, and of Richard Brown, a criminal trial lawyer. Donahue testified to his reasons for having declined the state's offer of a continuance for the purpose of obtaining a review by Gross of Sturner's slides. Brown gave his opinion that Donahue's failure to have the slides examined constituted ineffective assistance of counsel.

The habeas court rejected both of the petitioner's claims. With respect to the claim of unreliable medical evidence, the habeas court found that "Taff's examination of the slides prepared for Dr. Sturner was significant only with respect to the manner in which the hyoid bone was fractured. His opinion concurred with that of Dr. Gross, that the fracture occurred during the autopsy procedure." The habeas court reasoned that, if it chose to believe Taff's testimony in toto, it would be usurping the function of the jury at the petitioner's criminal trial, because "[a]s it unfolded, the trial of [the petitioner] could best be summarized as a battle of the experts" over the cause of death. The habeas court reasoned that it was for the jury to accept or reject, in whole or in part, any such expert testimony. The court concluded that Gross' opinion as to the cause of death had been rejected by the jury, and that Taff's conclusions did not constitute new evidence but were based on the same evidence that had been available at the trial. The court therefore rejected a review of the conflicting expert testimony as not properly within the scope of the writ of habeas corpus.

With respect to the claim of ineffective assistance of counsel, the habeas court found, on the basis of Donahue's testimony, that Donahue had exercised his judgment after weighing the pros and cons of securing a continuance for Gross to review the slides. The court concluded that (1) the petitioner had not proven by a preponderance of evidence that Donahue's performance had not been reasonably competent, and (2) even if that performance had been less than reasonably competent, the petitioner had not established that the failure to have either Gross or some other expert review the slides contributed to his conviction. Accordingly, the habeas court dismissed the petition.

The petitioner thereafter filed a petition for certification to appeal to the Appellate Court from the judgment of the habeas court, pursuant to General Statutes 52-470(b). In accordance with the certification granted by the habeas judge pursuant to 52-470, the two questions that the petitioner sought to have reviewed by the Appellate Court were: (1) "Did the habeas court err in its conclusion that it is not within the province of the habeas court to make a determination relative to the reliability/unreliability of a petitioner's trial evidence in order to decide a petitioner's claim of violation of due process?"; and (2) "Did the habeas court err in its conclusion that [the] petitioner's trial counsel was not ineffective in rejecting and/or failing to request a continuance in order to investigate certain scientific forensic evidence presented by the state?"

The Appellate Court first considered the petitioner's ineffective assistance of counsel claim. Although it rejected as legitimate strategic concerns Donahue's first three reasons for declining to seek or accept a continuance; see footnote 9; the court concluded that, considering the facts supporting the fourth and fifth reasons; see Summerville v. Warden, supra, 29 Conn. App. 174-76; "Donahue [had] exercised reasonable judgment in not accepting a continuance to investigate the evidence relied on by the state in the rebuttal portion of its case." Id., 174. The Appellate Court, therefore, affirmed the habeas court's rejection of the petitioner's claim of ineffective assistance of counsel. Id., 176.

The Appellate Court then turned to the petitioner's claim that, based on Taff's testimony, he had been denied a fair trial because the medical evidence presented at his trial regarding the cause of death was unreliable. The Appellate Court noted that the habeas court had not evaluated Taff's testimony because it had concluded that it lacked the authority on habeas corpus "to inquire into the sufficiency of the evidence or the resolution of the facts that supported the petitioner's conviction." Id., 177. Reading the petitioner's claim to be, not that his conviction was unsupported by sufficient evidence, but rather that Taff's testimony, which had not been presented at his trial, sufficiently undermined the conclusiveness of the jury's fact-finding process so as to mandate a new trial, the Appellate Court cast the issue as follows: "If this claim, that the medical evidence presented against him at trial was unreliable and therefore violated his right to a fair trial, is properly raised in a petition for a writ of habeas corpus, then we must remand the case to the habeas court for further consideration." Id., 178.

The Appellate Court concluded that, because the petitioner's claim was properly raised in a habeas corpus proceeding, and because the habeas court had not examined the merits of the petitioner's claim — i.e., the credibility of Taff's testimony and its likely effect on the jury's verdict — "and might have ruled differently had these merits been explored"; id., 180; the Appellate Court was required to "remand the case to the habeas court for further consideration of the merits of the petitioner's claim that his conviction was based on unreliable medical evidence." Id. The Appellate Court, therefore, ordered that, on the remand, the habeas court "carefully examine the new medical evidence bearing on the issue of the cause of the victim's death in order to determine the effect the new evidence would have on a jury in rendering its verdict"; id.; and that, in doing so, the habeas court "consider Taff's testimony in relation to the trial testimony considered by the jury . . . . If, after analyzing this evidence, the habeas court concludes that an injustice was done and that it is probable that a different result would be reached in a new trial, then the court must grant the writ." Id., 181. The Appellate Court gave the following reasons for this conclusion.

First, our habeas corpus statute, 52-470(a), requires the habeas court to "dispose of the case as law and justice require," and the petitioner's claim that no crime was committed "goes to the very essence of the constitutional guarantee of due process." Id., 179. Relying on Bunkley v. Commissioner of Correction, 222 Conn. 444, 460-61, 610 A.2d 598 (1992), the court reasoned that in order for a habeas corpus petitioner to demonstrate a fundamental unfairness or miscarriage of justice cognizable in a habeas corpus proceeding for a new trial, he must "show that he is burdened by an unreliable conviction." (Internal quotation marks omitted.) Summerville v. Warden, supra, 29 Conn. App. 179. Relying on Taborsky v. State, 142 Conn. 619, 116 A.2d 433 (1955), and Reilly v. State, 32 Conn. Sup. 349, 355 A.2d 324 (1976), the court reasoned that "[w]here new evidence undermines judicial confidence in the result reached such that it can be said that an injustice was likely done and that it is probable that a new trial would produce a different result, relief must be available through the writ of habeas corpus." Summerville v. Warden, supra, 29 Conn. App. 179.

Second, the Appellate Court relied on State v. Hammond, 221 Conn. 264, 268, 604 A.2d 793 (1992), for the proposition that "[o]ne cogent reason for overturning the verdict of a jury is that the verdict is based on conclusions that are physically impossible." The Appellate Court characterized the petitioner's evidence in these proceedings, aimed at establishing that no crime had been committed because the victim's death had not been the result of manual strangulation, as evidence that, "if found to be such that a jury might reasonably credit [it], indicates that the petitioner's conviction was based on a scientific improbability, if not an impossibility." Summerville v. Warden, supra, 29 Conn. App. 179. The Appellate Court continued: "The exculpatory evidence proffered at the habeas hearing raises a serious question of whether a jury could reasonably have concluded that the petitioner was guilty beyond a reasonable doubt had the new evidence been before it, along with the evidence already considered at trial. State v. Hammond, supra, 286-87. Because that is so, and because our jurisprudence mandates that we give effect to the presumption of innocence even in a postconviction proceeding, a remand is necessary so that Taff's testimony and the facts established and the inferences reasonably drawn therefrom can be evaluated by the habeas court." Summerville v. Warden, supra, 180. We thereafter granted the petitioner's and the respondent's petitions for certification. This appeal and cross appeal followed.

III

We first consider the question posed by the petitioner's petition for certification: "Did the Appellate Court correctly conclude that it should not decide the issue of whether an ineffective investigation by a defense expert witness in a fashion that impairs the petitioner's defense is impugned to the defense attorney?" We conclude that we improvidently granted the petition for certification regarding this issue, and we therefore decline to consider it.

Throughout these proceedings, the petitioner's presentation issue is a part of his claim under the second count of the petition for habeas corpus, namely, ineffective assistance of counsel. The petitioner's claim rests on the premise that at the petitioner's criminal trial Gross' failure, in the first instance, even before Sturner's testimony, to have microscopic slides prepared for purposes of forming his opinions and testifying thereto regarding the cause of the victim's death, constituted ineffective investigation by Gross as an expert witness. From this premise, the petitioner argues that Gross' ineffective investigation was attributable to Donahue, as the petitioner's attorney, and thereby constituted ineffective assistance of counsel. From these premises, the petitioner argues that the Appellate Court should have considered the question presented by his petition for certification.

Whatever the merits of such an argument may be in a case that presents it, it is clear from this record that this is not such a case. The claim that Gross, as an expert defense witness, performed his investigative function ineffectively, and that his inadequacy in that regard was attributable to the petitioner's counsel for purposes of a constitutional claim of ineffective assistance of counsel, cannot be gleaned from this record. It is not fairly within even a generous reading of any of the petitioner's various amended petitions, including the last petition, which was filed during the hearing in order to make his pleading conform to his proof. It was not litigated before the habeas court; it was not decided — or even referred to — by the habeas court in its memorandum of decision. Thereafter, the petitioner did not request the habeas court to articulate its decision further to consider such a claim. Finally, it is not within the questions that the petitioner requested the habeas court to certify for appellate review.

Under these circumstances, it is hardly surprising that the Appellate Court did not consider the petitioner's claim. We decline to do so as well.

IV

We turn next to the question posed by the respondent's petition for certification: "Did the Appellate Court have proper grounds for remanding this case to the habeas court for a consideration of expert testimony that was not presented at the petitioner's criminal trial?" The respondent argues that the Appellate Court (1) applied improper standards of habeas corpus review of final convictions, (2) improperly afforded the petitioner the presumption of innocence in this collateral attack on the petitioner's conviction, and (3) improperly characterized Taff's testimony as new medical evidence that was sufficient to undermine confidence in the reliability of the jury's verdict in the petitioner's criminal trial. We agree.

The standards that generally govern a habeas corpus petition seeking a new trial are well established. "The principal purpose of the writ of habeas corpus is to serve as a bulwark against convictions that violate fundamental fairness. Engle v. Isaac, 456 U.S. 107, 126, 102 S.Ct. 1558, 71 L.Ed.2d 783 (1982), quoting Wainwright v. Sykes, 433 U.S. 72, 97, 97 S.Ct. 2497, 53 L.Ed.2d 594 (1977) (Stevens, J., concurring). This court has taken the same view. To mount a successful collateral attack on his conviction, a prisoner must demonstrate a miscarriage of justice or other prejudice and not merely an error which might entitle him to relief on appeal. Hill v. United States, 368 U.S. 424, 428, 82 S.Ct. 468, 7 L.Ed.2d 417, reh. denied, 369 U.S. 808, 82 S.Ct. 640, 7 L.Ed.2d 556 (1962). D'Amico v. Manson, 193 Conn. 144, 156-57, 476 A.2d 543 (1984); see also Bowers v. Warden, 19 Conn. App. 440, 441, 562 A.2d 588, cert. denied, 212 Conn. 817, 565 A.2d 534 (1989). In order to demonstrate such a fundamental unfairness or miscarriage of justice, the petitioner should be required to show that he is burdened by an unreliable conviction." (Internal quotation marks omitted.) Bunkley v. Commissioner of Correction, supra, 222 Conn. 460-61.

It is important to clarify initially what is not, and what is, involved in our consideration of this issue. The petitioner does not claim that the evidence of guilt at his criminal trial was insufficient. The Appellate Court rejected that claim in his original appeal; State v. Summerville, supra, 13 Conn. App. 175; and habeas corpus is not designed to relitigate that issue. Payne v. Robinson, 207 Conn. 565, 568, 541 A.2d 504, cert. denied, 488 U.S. 898, 109 S.Ct. 242, 102 L.Ed.2d 230 (1988); Cajigas v. Warden, 179 Conn. 78, 81, 425 A.2d 571 (1979); Vena v. Warden, 154 Conn. 363, 365, 225 A.2d 802 (1966).

The petitioner's claim is instead that he is entitled by way of habeas corpus to a new trial because the evidence at his criminal trial was medically unreliable. That claim, however, is independent of and unrelated to any claim that his conviction was otherwise affected by some antecedent constitutional error that affected his trial. Thus, in the context of this issue he cannot claim that his criminal trial was unfair because, for example, his counsel was ineffective, or evidence was unconstitutionally introduced or excluded in that trial. We are not confronted, therefore, with a claim that he is burdened by an unreliable conviction resulting from such an antecedent constitutional violation. Compare, e.g., Bunkley v. Commissioner of Correction, supra, 222 Conn. 444 (habeas corpus claim for new trial based on constitutional claim of ineffectiveness of appellate counsel); Phillips v. Warden, 220 Conn. 112, 595 A.2d 1356 (1991) (habeas corpus claim for new trial based on constitutional claim of ineffectiveness of trial counsel flowing from actual conflict of interest).

The petitioner's claim is, as he states, one of "factual innocence." On the basis of Taff's testimony that the cause of death of the victim was not asphyxiation resulting from manual strangulation, but acute cocaine intoxication, the petitioner claims that he is the victim of a miscarriage of justice because "no crime was committed." (Emphasis in original.) In support of this claim, he argues that the Appellate Court was correct in its analysis of his claim because, as that court concluded: (1) under the circumstances of this case, he is entitled to the presumption of innocence; (2) Taff's testimony constituted new evidence requiring a new trial; and (3) Taff's testimony in the habeas court, "juxtaposed against the medical testimony presented at the criminal trial," indicates that the petitioner's "conviction was based upon a scientific improbability, if not an impossibility." (Internal quotation marks omitted.) Because the petitioner's arguments mirror, and share the same assumptions as, the reasoning of the Appellate Court, and because on certification our focus is ordinarily on the opinion of that court; Cahn v. Cahn, 225 Conn. 666, 671, 626 A.2d 296 (1993); State v. Beckenbach, 198 Conn. 43, 47, 501 A.2d 752 (1985); we address those arguments and assumptions.

The foundational question is whether habeas corpus permits the granting of a new trial pursuant to a petitioner's claim of actual innocence, unadorned by an antecedent showing of a constitutional violation that affected the fairness of his criminal trial. We conclude that it does.

Habeas corpus is the ultimate inquiry into the fundamental fairness of a criminal proceeding. See, e.g., Lozada v. Warden, 223 Conn. 834, 840, 613 A.2d 818 (1992); Safford v. Warden, 223 Conn. 180, 190, 612 A.2d 1161 (1992); Bunkley v. Commissioner of Correction, supra, 222 Conn. 460. In Murray v. Carrier, 477 U.S. 478, 106 S.Ct. 2639, 91 L.Ed.2d 397 (1986), the United States Supreme Court held that the cause and prejudice standard applies to procedural defaults by state appellate counsel for purposes of federal habeas corpus jurisprudence. The court carved out an exception, however, for certain claims of actual innocence: "Accordingly, we think that in an extraordinary case, where a constitutional violation has probably resulted in the conviction of one who is actually innocent, a federal habeas corpus court may grant the writ even in the absence of a showing of cause for the procedural default." Id., 496. Similarly, this court, in holding that the cause and prejudice standard applies to appellate procedural defaults for purposes of our own habeas corpus jurisprudence, made clear that our holding was not meant to preclude "a substantial claim of innocence in fact." Jackson v. Commissioner of Correction, 227 Conn. 124, 132 n. 7, 629 A.2d 413 (1993).

We now hold, therefore, what we implied in Jackson, namely, that a substantial claim of actual innocence is cognizable by way of a petition for a writ of habeas corpus, even in the absence of proof by the petitioner of an antecedent constitutional violation that affected the result of his criminal trial. This holding is consistent with the mandate of 52-470(a) that the habeas court "dispose of the case as law and justice require." Even the strong interest in the finality of judgments, and the state's interest in retrying a defendant with reasonably fresh evidence, does not require the continued imprisonment of one who is actually innocent. This holding is also consistent with our prior statements that habeas corpus is designed to remedy fundamental miscarriages of justice. See, e.g., D'Amico v. Manson, supra, 193 Conn. 144. The continued imprisonment of one who is actually innocent would constitute a miscarriage of justice.

Contrary to the petitioner's argument, however, such an inquiry, as a collateral attack on a conviction, cannot rely on the presumption of innocence because that presumption does not survive a judgment of conviction. It is undoubtedly true that "[a] person when first charged with a crime is entitled to a presumption of innocence, and may insist that his guilt be established beyond a reasonable doubt. In re Winship, 397 U.S. 385 [ 397 U.S. 358], 90 S.Ct. 1068, 25 L.Ed.2d 368 (1970)." Herrera v. Collins, ___ U.S. ___, 113 S.Ct. 853, 859, 122 L.Ed.2d 203 (1993). It is also true that other constitutional provisions, such as the right to counsel, the right of confrontation, the right to compulsory process, the requirement of proof beyond a reasonable doubt, and the right to exculpatory evidence, "also have the effect of ensuring against the risk of convicting an innocent person." Id. "All of these constitutional safeguards . . . make it more difficult for the State to rebut and finally overturn the presumption of innocence which attaches to every criminal defendant." Id., 860.

The presumption of innocence, however, does not outlast the judgment of conviction at trial. "Once a defendant has been afforded a fair trial and convicted of the offense for which he was charged, the presumption of innocence disappears. Cf. Ross v. Moffitt, 417 U.S. 600, 610, 94 S.Ct. 2437, 41 L.Ed.2d 341 (1974) (`The purpose of the trial stage from the State's point of view is to convert a criminal defendant from a person presumed innocent to one found guilty beyond a reasonable doubt'). Here, it is not disputed that the State [has] met its burden of proving at trial that petitioner was guilty of [manslaughter in the first degree] beyond a reasonable doubt. Thus, in the eyes of the law, [the] petitioner does not come before the Court as one who is `innocent,' but on the contrary as one who has been convicted by due process of law of [manslaughter in the first degree]." Id.

Any other conclusion would be inconsistent with the fact that our habeas corpus jurisprudence places a heavy burden on the petitioner to establish that, notwithstanding his conviction, he is entitled to a new trial. Lubesky v. Bronson, 213 Conn. 97, 110, 566 A.2d 688 (1989); Myers v. Manson, 192 Conn. 383, 387, 472 A.2d 759 (1984). Put another way, it would be anomalous to say that one who is presumed to be innocent nonetheless bears a heavy burden to prove that he is entitled to a new trial because he is actually innocent. If the presumption of innocence means anything, it means that one who is clothed with it does not bear the burden of establishing his innocence. Furthermore, attaching the presumption of innocence to a habeas corpus petitioner would be inconsistent with the well recognized difficulties and costs often occasioned by the issuance of a writ of habeas corpus years after the original conviction. See Johnson v. Commissioner of Correction, 218 Conn. 403, 589 A.2d 1214 (1991). Thus, we reject the conclusion that the petitioner was entitled, in these proceedings, to the presumption of innocence.

We also do not share the assumption, engaged in by both the petitioner and the Appellate Court, that underlies the view that Taff's testimony, if credited, constituted new evidence requiring the habeas court to grant a new trial. That assumption is that the standards for a habeas court in ruling on a petition for a writ of habeas corpus based on a claim of actual innocence are the same as the standards for a trial court in ruling on a petition for a new criminal trial on the ground of newly discovered evidence, pursuant to General Statutes 54-95(a) and 52-270.

The petitioner relies, for his claim that Taff's testimony constituted new evidence of actual innocence, on cases decided upon petitions for new trials because of newly discovered evidence. See, e.g., Taborsky v. State, 142 Conn. 619, 116 A.2d 433 (1955); Reilly v. State, 32 Conn. Sup. 349, 355 A.2d 324 (1976). The primary test for determining whether a new trial should be granted because of newly discovered evidence "is whether an injustice was done and whether it is probable that on a new trial a different result would be reached." Taborsky v. State, supra, 623. The plaintiff has the burden of proving the probability of a different result. Id. Furthermore, the new evidence must not have been discoverable and producible at the original trial by the exercise of due diligence, and must not be cumulative. Id. Even cumulative evidence, however, "can be grounds for a new trial if it appears reasonably certain that injustice has been done in the judgment rendered and that the result of a new trial will probably be different. Pass v. Pass, 152 Conn. 508, 512 [ 208 A.2d 753 (1965)]." (Internal quotation marks omitted.) Reilly v. State, supra, 355. Furthermore, the scope of review of a trial court's decision to grant a new trial on the basis of newly discovered evidence is limited to whether the trial court abused its discretion. Taborsky v. State, supra, 623.

A critical limitation on the exercise of the trial court's discretion in passing upon such a petition for a new trial, however, is the statute of limitations. "No petition for a new trial in any civil or criminal proceeding shall be brought but within three years next after the rendition of the judgment or decree complained of." General Statutes 52-582. The three year period begins to run from the date of rendition of judgment by the trial court; Varley v. Varley, 181 Conn. 58, 434 A.2d 312 (1980); which, in a criminal case, is the date of imposition of the sentence by the trial court. State v. Coleman, 202 Conn. 86, 89, 519 A.2d 1201 (1987).

The three year statute of limitations on a petition for a new trial based on newly discovered evidence is the product of the legislature's balancing of the interests of the petitioner against the interests of the public and the state. The petitioner's interest is in attempting to establish that he is probably not guilty and that, therefore, the verdict in his criminal trial should be overturned. The state's interests are in preserving the finality of judgments, in not degrading the properly prominent place given to the original trial as the forum for deciding the question of guilt or innocence within the limits of human fallibility, and in the fact that in many cases an order for a new trial may in reality reward the accused with complete freedom from prosecution because of the debilitating effect of the passage of time on the state's evidence. Bunkley v. Commissioner of Correction, supra, 222 Conn. 461-63.

Indeed, one of the principal purposes of any statute of limitations is to enhance the reliability of fact-finding, based upon the common sense notions that the unreliability of fact-finding increases with the passage of time; see Herrera v. Collins, supra, 113 S.Ct. 862 ("the passage of time only diminishes the reliability of criminal adjudications"); McCleskey v. Zant, 499 U.S. 467, 111 S.Ct. 1454, 113 L.Ed.2d 517 (1991); United States v. Smith, 331 U.S. 469, 476, 67 S.Ct. 1330, 91 L.Ed. 1610 (1947); and that it is wise public policy to minimize that degree of unreliability by barring the fact-finding process after the applicable limitations period. See Bunkley v. Commissioner of Correction, supra, 222 Conn. 462.

Thus, for a petition for a new trial, within the three year limitations period, the petitioner's interests trump those of the public and the state. Beyond that period, however, the interests of the public and the state trump those of the petitioner.

Principally because of the absence of any statute of limitations governing the writ of habeas corpus; United States v. Smith, supra, 331 U.S. 476; the standards governing the issuance of the writ based on a claim of actual innocence are not, however, necessarily the same as those governing a petition for a new trial based upon newly discovered evidence. Employing the same standard for both petitions would ignore the legislative determination embodied in the statute of limitations. The principal purpose of the writ of habeas corpus is to serve as a bulwark against violations of fundamental fairness. Bunkley v. Commissioner of Correction, supra, 222 Conn. 460-61. Whether there has been such a violation must be determined, not only with regard to the petitioner's claim, but also with regard to the effect of the issuance of the writ on the strong interest in the finality of judgments; Myers v. Manson, supra, 192 Conn. 387; and the other interests embodied in the statute of limitations. See Engle v. Isaac, supra, 456 U.S. 126; Bunkley v. Commissioner of Correction, supra, 461-62.

We have, therefore, imposed on a habeas corpus petitioner certain requirements that reflect these policy interests. For example, we have imposed a heavy burden of proof on the petitioner to establish that he is entitled to a new trial. Lubesky v. Bronson, supra, 213 Conn. 110. We have also adopted the"cause and prejudice" standard for the reviewability in a habeas corpus proceeding of constitutional claims not adequately preserved at trial; Johnson v. Commissioner of Correction, supra, 218 Conn. 409; or on appeal; Jackson v. Commissioner of Correction, supra, 227 Conn. 130; because of a procedural default.

Those requirements, which stem largely from the fact that a habeas corpus petition may properly be brought at any time, rest in significant part on the costs to the public interests that are incurred when the state is required to retry a defendant many years after the events in question. See Johnson v. Commissioner of Correction, supra, 218 Conn. 403. The wholesale transplanting of the petition for a new trial standard to a habeas corpus petition based on a claim of actual innocence would not give due respect to those considerations. The petitioner who thinks that there is newly discovered evidence sufficient to overturn his verdict would have no incentive to bring that evidence before the court within the three year limitations period, and there would be no consequence of his failure to do so. Thus, just as a habeas corpus petition may not be employed as a substitute for a direct appeal; Payne v. Robinson, supra, 207 Conn. 568; a habeas corpus petition is not a surrogate for a time barred petition for a new trial.

Similarly, the standard that we announced in Bunkley v. Commissioner of Correction, supra, 222 Conn. 444, for granting a new trial pursuant to a writ of habeas corpus based on ineffectiveness of counsel, is not appropriate for this case. That standard is, in general terms, "whether there was a reasonable probability that, but for [the petitioner's] counsel's failure, the verdict would have been different." Id., 457. The rationale for that standard, however, does not support its transfer to this type of case.

That rationale is that, because of the antecedent, constitutional ineffectiveness of the petitioner's counsel in the original criminal proceedings, there was a breakdown of the traditional adversarial process on which we rely to produce just results. Therefore, precisely because of the breakdown of that traditional adversary process, our confidence in the reliability of the verdict in the criminal trial is undermined in a case in which the petitioner was hampered by constitutionally ineffective counsel at that trial. Based on that rationale, prejudice in the habeas corpus sense is established solely on the basis of a reasonable probability that, but for that ineffectiveness, the outcome would have been different.

That rationale is absent from this case, however, because in this case the petitioner's trial counsel was not ineffective, and therefore there was no breakdown of the adversarial process sufficient to undermine our confidence in the reliability of the verdict. Thus, this case differs from Bunkley in the significant respect that, whereas in Bunkley the petitioner's claim on habeas corpus was twofold — (1) his counsel was ineffective, and (2) because of that ineffectiveness the verdict should be overturned and a new trial granted — in this case the petitioner lacks the first factor, and as a result, his foundation for the second factor is significantly weakened.

The petitioner's claim, to the contrary, is solely that, despite the fairness of the fact-finding process in his criminal trial, he is entitled to a new trial because, based on the evidence he now adduces, that fact-finding process was flawed in that the prior evidence was inherently unreliable. This critical difference between the two cases, and the roots that the Bunkley standard has in the unreliability of the first trial's factual outcome — roots that the petitioner's claim in this case does not share — persuade us that the Bunkley standard is inadequate to respond to the case of a claim of actual innocence unconnected to an antecedent constitutional violation that affected the reliability of the outcome of the first trial.

Both the petition for a new trial standard and the Bunkley standard rely essentially on a determination by the reviewing court — either the trial court passing on a petition for a new trial, or a habeas court passing on a claim of ineffectiveness of counsel — that, considering the evidence and claims now brought before it, together with the evidence produced at the original trial, there is a probability of a different result. Because neither of those standards appropriately fits the interests at stake in this type of habeas petition, we conclude that the standard should be more demanding than a probability of a different result. None of our prior habeas corpus jurisprudence, however, supplies us with a ready standard for this type of case.

The issue then becomes the determination of the correct standard. Such a determination must recognize the tension inherent in the mandate of the statute that the habeas court "dispose of the case as law and justice require." General Statutes 54-470 [ 52-470](a). What "law and justice require" is not a one-sided question. The standard must strike an appropriate balance between, on one hand, the risk that an actually innocent person may be incarcerated, despite his conviction after a fair trial, and, on the other hand, the risk that an actually guilty person, fairly convicted, may nonetheless be set free years later, principally because of the effect of the passage of time on the state's evidence and on the reliability of the fact-finding process.

The issue of the determination of the correct standard for this type of case can be divided into two components. The first question is: what is the legal standard that must be met by a habeas corpus petitioner claiming actual innocence in order to gain a new trial at which his guilt or innocence will again be determined? Put another way, what does "a substantial claim of actual innocence" mean in this context? The second question is: applying that standard, what evidence adduced by such a petitioner claiming actual innocence is sufficient to trigger the requirement of the habeas court to evaluate that evidence, together with and in light of the evidence produced at the petitioner's criminal trial, and, as a result of that evaluation, to permit the habeas court to issue the writ? We conclude, under the circumstances of this case, that we need not answer the first question, and need not elaborate on the second question, because the petitioner's evidence was insufficient under any of the standards presented to us by the parties in this case or by other appropriate habeas corpus jurisprudence.

We turn for guidance to other standards that have been suggested for the resolution of this issue, namely, the standard that a habeas petitioner who claims actual innocence must meet in order to gain a new trial. The petitioner in effect offers only the standard applicable to a petition for a new trial for newly discovered evidence, which we have rejected. The respondent suggests that such a writ issue "only upon the most compelling evidence that a miscarriage of justice has occurred." (Emphasis added.)

In a slightly different context, the United States Supreme Court has wrestled with this problem. In Herrera v. Collins, supra, 113 S.Ct. 853, the court addressed a claim, in a federal habeas corpus proceeding, by a petitioner who had been convicted of two murders and sentenced to death by the Texas courts. In his federal petition filed approximately ten years after his conviction, he claimed, based on certain affidavits that he filed, that he was innocent of the murders and that the eighth and fourteenth amendments to the United States constitution "prohibit the execution of a person who is innocent of the crime for which he was convicted." Id., 859. Thus, he sought either a new trial or, in the alternative, that his death sentence be vacated. Id., 864.

The majority of the court assumed, arguendo, "that in a capital case a truly persuasive demonstration of `actual innocence' made after trial would render the execution of a defendant unconstitutional, and warrant federal habeas relief if there were no state avenue open to process such a claim." (Emphasis added.) Id., 869. On the basis of that assumption, the majority of the court held that, in part because of "the enormous burden that having to retry cases based on often stale evidence would place on the States, the threshold showing for such an assumed right would necessarily be extraordinarily high." (Emphasis added.) Id. The majority held that the affidavits filed by the petitioner did not meet that standard. Id., 869-70.

Justice O'Connor, joined by Justice Kennedy, concurred separately. They agreed that federal habeas relief based upon claims of actual innocence must be "reserved for extraordinarily high and truly persuasive demonstration[s] of actual innocence that cannot be presented to state authorities . . . ." (Emphasis added; internal quotation marks omitted.) Id., 874 (O'Connor, J., concurring.). They also agreed that the petitioner's affidavits fell far short of this showing. Id.

Justice White, concurring in the judgment, agreed with the assumption that a persuasive showing of actual innocence, although made after the time required by law for presentation of newly discovered evidence, would render an execution unconstitutional. Justice White, however, formulated the standard as follows: "To be entitled to relief . . . [the] petitioner would at the very least be required to show that based on proffered newly discovered evidence and the entire record before the jury that convicted him, no rational trier of fact could [find] proof of guilt beyond a reasonable doubt." (Emphasis added; internal quotation marks omitted.) Id., 875 (White, J., concurring.). Justice White also agreed that the petitioner's affidavits fell far short of meeting that standard. Id.

The California Supreme Court has articulated a similarly high standard. In In re Clark, 5 Cal.4th 750, 855 P.2d 729 (1993), ruling on a habeas petitioner's claim of, inter alia, actual innocence based on newly discovered evidence; id., 734; the court articulated the following standard: "[W]hether raised in a petition for [a] writ of habeas corpus or by coram nobis, newly discovered evidence is a basis for relief only if it undermines the prosecution's entire case. It is not sufficient that the evidence might have weakened the prosecution case or presented a more difficult question for the judge or jury . . . . [A] criminal judgment may be collaterally attacked on the basis of newly discovered evidence only if the new evidence casts fundamental doubt on the accuracy and reliability of the proceedings. . . . [S]uch evidence, if credited, must undermine the entire prosecution case and point unerringly to innocence or reduced culpability." (Citations omitted; emphasis added; internal quotation marks omitted.) Id., 739.

Applying these various standards to the petitioner's evidence, we conclude that, under any one of them, Taff's testimony was insufficient to trigger an evaluation of it by the habeas court for the purpose of determining whether the petitioner had made a showing of actual innocence sufficient to require a new trial. First, contrary to the characterization of Taff's testimony by the Appellate Court, that testimony did not indicate "that the petitioner's conviction was based on a scientific improbability, if not an impossibility." In this respect, we disagree with the Appellate Court's analogy of Taff's testimony to the scientific evidence that we considered in State v. Hammond, supra, 221 Conn. 264. As we have indicated; see footnote 13; in Hammond it was undisputed, based on uncontroverted blood typing and DNA evidence, that it was scientifically impossible for the defendant to have committed the sexual assault in question.

The same cannot be said of Taff's testimony. That testimony amounted to nothing more than a fourth expert opinion derived from an interpretation of the underlying autopsy data that Katsnelson, Gross and Sturner had already interpreted. That is not the kind of evidence that renders prior expert opinions as to the cause of death scientifically impossible or improbable. Indeed, if it were, "[t]he ultimate result would be a never-ending battle of [pathologists] appointed [or retained] as experts for the sole purpose of discrediting a prior [pathologist's] diagnosis." Silagy v. Peters, 905 F.2d 986, 1013 (7th Cir. 1990), cert. denied, 498 U.S. 1110, 111 S.Ct. 1024, 112 L.Ed.2d 1106 (1991).

Second, Taff's interpretation was based on viewing less of the underlying autopsy data than the interpretations of the three pathologists who had preceded him. Katsnelson, Gross and Sturner had each examined the victim's hyoid bone and the wet tissue specimens of her laryngeal area. Katsnelson had performed the autopsy and had seen the hyoid bone separation before extracting that bone, as well as the actual crescent shaped mark on her neck. Taff, however, had seen only the photographs of those areas as well as the same slides seen by Sturner. Furthermore, he had formed his opinion without knowing that he petitioner had given inconsistent statements regarding the events in question, that the petitioner had stated that he and the victim had been fighting, and that there had been loud noises emanating from their room that were consistent with a fight between them.

Third, Taff's testimony, while differing in some respects from the testimony of Gross, the defense expert at trial, simply reinforced Gross' testimony in certain other, important respects. Both Gross and Taff: (1) minimized the crescent shaped mark by attributing it to causes other than manual strangulation; (2) opined that the hemorrhages in the victim's eyelid were not petechial; (3) attributed the hemorrhages in the sternocleidomastoid and sternohyoid muscles to causes other than manual strangulation; (4) stated that the separation of the hyoid bone was artifactual; (5) attributed the hemorrhages in the epiglottis area to intubation during resuscitation efforts, rather than to manual strangulation; (6) relied in part on the absence of external signs of injury; and (7) gave acute cocaine intoxication as the cause of death. Thus, in large part, Taff's testimony simply repeated, sometimes in the same terms and sometimes in different terms, the testimony of Gross that the petitioner's jury had already rejected as sufficient to raise a reasonable doubt as to his guilt.

By any of the standards for a substantial showing of actual innocence that we have postulated — the most compelling evidence of actual innocence; a truly persuasive demonstration of actual innocence; an extraordinarily high and truly persuasive demonstration of actual innocence; evidence on which no rational trier of fact could find proof of guilt beyond a reasonable doubt; or evidence that casts fundamental doubt on the accuracy and reliability of the original verdict, and that, if credited, undermines the entire prosecution case and points unerringly to innocence — the petitioner's evidence falls short. It was, therefore, unnecessary for the habeas court to evaluate it for the purpose of determining whether, taken together with and in light of the trial evidence, the writ of habeas corpus should issue on the ground that the petitioner was actually innocent.