Colo. R. Evid. 702

As amended through Rule Change 2024(18), effective October 2, 2024

Rule 702 - Testimony by Experts

If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.

CRE 702

Annotation Law reviews. For article, "Selecting an Expert Witness", see 12 Colo. Law. 1464 (1983). For review, "Admissibility of Thermography: Objective Evidence or a Mystical Procedure", see 65 Den. U. L. Rev. 295 (1988). For article, "Hearsay as a Basis for Opinion Testimony", see 17 Colo. Law. 2337 (1988). For article, "DNA: The Eyewitness of the Future", see 18 Colo. Law. 1333 (1989). For article, "Rule 702: Admissibility of Expert Testimony Regarding Eyewitness Identification", see 21 Colo. Law. 927 (1992). For article, "Introduction of Scientific Evidence in Criminal Cases", see 22 Colo. Law. 273 (1993). For article, "Opinion Testimony", see 22 Colo. Law. 1185 (1993). For article, "The Misuse and Abuse of Psychological Experts in Court", see 23 Colo. Law. 2757 (1994). For article, "Evaluating Recovered Memories of Trauma as Evidence", see 25 Colo. Law. 1 (January 1996). For article, "Rule 702: Admissibility of Expert Testimony", see 30 Colo. Law. 55 (November 2001). For article, "Limits on Attorney-Expert Opinions in Jury Trials Under C.R.E. 403, 702, and 704 ", see 31 Colo. Law. 53 (March 2002). For article, "Tips for Working With Evidence in Domestic Relations Cases", see 31 Colo. Law. 87 (June 2002). For article, "Polygraph Examinations: Admissibility and Privilege Issues", see 31 Colo. Law. 69 (November 2002). For article, "Challenging the Unreliable Damages Expert-Part I", see 32 Colo. Law. 119 (October 2003). For article, "Challenging the Unreliable Damages Expert-Part II", see 32 Colo. Law. 103 (November 2003). For article, "Colorado's Certificate of Review Statute: Considerations in Professional Negligence Cases", see 33 Colo. Law. 11 (February 2004). For article, "The Admissibility of Expert 'Profile Evidence'", see 33 Colo. Law. 53 (March 2004). For article, "Rules 701 and 702: Boundary Between Lay and Expert Opinion Testimony", see 34 Colo. Law. 53 (July 2005). For article, "Using Experts to Aid Jurors in Assessing Child Witness Credibility", see 35 Colo. Law. 65 (August 2006). This rule governs a trial court's determination regarding the admissibility of expert testimony. When proposed expert testimony involves experience-based specialized knowledge, the court must consider whether the testimony will be helpful to the jury and whether the witness is qualified to render an expert opinion on the subject in question. Meier v. McCoy, 119 P.3d 519 (Colo. App. 2004). Determination of expert within court's discretion. The trial court has wide discretion in determining whether the requirements to qualify a witness as an expert are met. Connell v. Sun Exploration & Prod. Co., 655 P.2d 426 (Colo. App. 1982). Matter of the qualification of expert witness is discretionary with the trial court. White v. People, 175 Colo. 119, 486 P.2d 4 (1971); People v. Tidwell, 706 P.2d 438 (Colo. App. 1985); People v. Koon, 724 P.2d 1367 (Colo. App. 1986); People v. Williams, 790 P.2d 796 (Colo. 1990). The court should consider the expert's experience of the time of trial, not on the date of the alleged malpractice. Durkee v. Oliver, 714 P.2d 1330 (Colo. App. 1986); People v. Braley, 879 P.2d 410 (Colo. App. 1993). The trial court determines the qualification of witnesses and has discretion to admit expert witness testimony. Eggert v. Mosler Safe Co., 730 P.2d 895 (Colo. App. 1986). The qualification of an expert is a matter within the sound discretion of the trial judge. People v. Chavez, 182 Colo. 216, 511 P.2d 883 (1973); People v. Lomanaco, 802 P.2d 1143 (Colo. App. 1990). The qualification of expert witness to competently testify on a matter of opinion is one of judicial discretion. People v. DeLuna, 183 Colo. 163, 515 P.2d 459 (1973). The qualification of an expert witness to testify is within the trial court's discretion and will not be disturbed absent an abuse of that discretion. Meier v. McCoy, 119 P.3d 519 (Colo. App. 2004). The competency of an expert is for the trial court to determine. People v. Anderson, 184 Colo. 32, 518 P.2d 828 (1974). Whether opinion testimony is within a witness' expertise generally is a matter addressed to the sound discretion of the court. People v. Gomez, 632 P.2d 586 (Colo. 1981). Trial court has broad discretion to determine the admissibility of expert testimony pursuant to this section. People v. Fasy, 820 P.2d 1314 (Colo. 1992). Trial court has discretion in determining the qualifications of an expert and the admissibility of expert evidence, and the court's ruling will not be disturbed absent an abuse of discretion. Baird v. Power Rental Equip., Inc., 191 Colo. 319, 552 P.2d 494 (1976); Klein v. State Farm Mut. Auto. Ins. Co., 948 P.2d 43 (Colo. App. 1997). Court's decision not disturbed absent abuse. A court's decision to allow a witness to testify as an expert will not be disturbed without a clear showing of an abuse of discretion. White v. People, 175 Colo. 119, 486 P.2d 4 (1971); People v. Hankin, 179 Colo. 70, 498 P.2d 1116 (1972); McCune v. People, 179 Colo. 262, 499 P.2d 1184 (1972); People v. Drumright, 181 Colo. 137, 507 P.2d 1097 (1973); People v. Anderson, 184 Colo. 32, 518 P.2d 828 (1974); Bd. of Comm'rs v. Fixed Base Operators, 939 P.2d 464 (Colo. App. 1997); People v. Bornman, 953 P.2d 952 (Colo. App. 1997). The sufficiency of foundation evidence to establish qualifications and knowledge of a witness to entitle him to express an opinion is a question for the trial court's determination, and in the absence of a showing of abuse of discretion this determination will not be overturned. People v. Jiminez, 187 Colo. 97, 528 P.2d 913 (1974). The discretion of the trial judge over the scope of expert testimony will not be disturbed on review absent a clear showing of abuse. People v. Davis, 187 Colo. 16, 528 P.2d 251 (1974); People v. Jensen, 747 P.2d 1247 (Colo. 1987). The determination of whether a witness is qualified to render an expert opinion is committed to the discretion of the trial court, and will not be disturbed on review unless that discretion is abused. People v. District Court, 647 P.2d 1206 (Colo. 1982). The trial court has discretion to rule upon the qualifications of expert witnesses and unless that discretion is abused its decision will not be disturbed on appeal. Stone v. Caroselli, 653 P.2d 754 (Colo. App. 1982). Trial court not required to make specific finding that witness is qualified as an expert. People v. Lomanaco, 802 P.2d 1143 (Colo. App. 1990). Disqualification of experts based on a conflict of interest is governed by a two-part test. First, whether it was objectively reasonable for the party to conclude that a confidential relationship existed with an expert consultant. Second, whether any confidential or privileged information was disclosed by that party to the expert consultant. In re Page, 70 P.3d 579 (Colo. App. 2003). A confidential relationship may arise if: (1) One party has taken steps to induce another to believe that it can safely rely on the first party's judgment or advice; (2) one party has gained the confidence of the other and purports to act or advise with the other's interest in mind; or (3) the parties' relationship is such that one is induced to relax the care and vigilance that ordinarily would be exercised in dealing with a stranger. In re Page, 70 P.3d 579 (Colo. App. 2003). Rule does not require previous qualification as an expert or that the proposed expert belong to any particular organization. White v. People, 175 Colo. 119, 486 P.2d 4 (1971); People v. Bornman, 953 P.2d 952 (Colo. App. 1997). Trial court inappropriately admitted lay testimony of investigating police officer as to experimentation with respect to and reconstruction of the incident without qualifying the officer as an expert witness. The officer's testimony involved more than common experience and required practical knowledge of a scientific, technical, or specialized nature. Admission of the testimony constitutes harmless error, however, and does not require reversal. People v. Stewart, 55 P.3d 107 (Colo. 2002). Trial court improperly admitted expert testimony of police officers concerning methamphetamine amounts, production chemicals, and manufacture under the guise of lay testimony. The testimony required specialized knowledge and training and, thus, was subject to the expert witness requirements of this rule. People v. Veren, 140 P.3d 131 (Colo. App. 2005). Trial courts possess broad discretion to allow or prohibit testimony by expert witnesses in criminal cases and an exercise of that discretion will not be overturned absent a showing of manifest error. People v. Lanari, 926 P.2d 116 (Colo. App. 1996). Trial court properly concluded that a witness was not qualified to give expert testimony on the use of force by law enforcement officers effecting an arrest when the witness had never (1) been employed in a law enforcement field, (2) participated professionally in a determination of what force a police officer may use in making an arrest, (3) arrested anyone, (4) completed a police officer training course, or (5) been retained by a police department to teach use of force. Meier v. McCoy, 119 P.3d 519 (Colo. App. 2004). This rule requires a two-tiered analysis for determining the reliability and validity of the underlying substance of an expert's opinion and a trial court must balance the reliability of the scientific principles upon which the testimony rests and the likelihood that the introduction of the evidence may overwhelm or mislead the jury. Colwell v. Mentzer Inv., Inc., 973 P.2d 631 (Colo. App. 1998); Schultz v. Wells, 13 P.3d 846 (Colo. App. 2000). In exercising its discretion under this rule, the court should consider numerous factors, including the nature and extent of evidence in the case, the expertise of the proposed witness, the sufficiency and extent of the foundational evidence upon which the expert witness' ultimate opinion is to be based, and the scope and content of the opinion itself. People v. Lanari, 926 P.2d 116 (Colo. App. 1996); People v. Lesslie, 939 P.2d 443 (Colo. App. 1996); People v. Masters, 33 P.3d 1191 (Colo. App. 2001), aff'd, 59 P.3d 979 (Colo. 2002). Lanari factors applied and admission of proffered expert testimony properly denied in People v. Miller, 981 P.2d 654 (Colo. App. 1998). This rule provides a more lenient standard for the admission of opinion evidence than does the test originally developed in Frye v. United States. The rule allows the admission of scientific evidence if such evidence will assist the jury in understanding the evidence or determining a fact at issue. DNA identification testimony in sexual assault case admissible under the rule and under Frye. People v. Fishback, 829 P.2d 489 (Colo. App. 1991), aff'd, 851 P.2d 884 (Colo. 1993). This rule represents the appropriate standard for determining the admissibility of scientific evidence, rather than the test developed in Frye v. United States. Under the standard established in this rule, the trial should focus on the reliability and relevance of the scientific evidence and determine the reliability of the scientific principles, the qualifications of the witness, and the usefulness of the testimony to the jury. In determining the reliability and relevance of the evidence, the court should apply a broad inquiry and consider the totality of the circumstances in each specific case, considering a wide range of factors. Because the applicable standard is so liberal, the court should also apply its discretionary authority under C.R.E. 403 to ensure the probative value of the evidence is not substantially outweighed by unfair prejudice. People v. Shreck, 22 P.3d 68 (Colo. 2001); Masters v. People, 59 P.3d 979 (Colo. 2002); People v. Rector, 248 P.3d 1196 (Colo. 2011). Trial court has discretion to decide whether to conduct an evidentiary hearing when a party requests a Shreck analysis. A court is not required to conduct an evidentiary hearing under Shreck provided it has before it sufficient information to make specific findings under C.R.E. 403 and this rule about the reliability of the scientific principles involved, the expert's qualification to testify to such matters, the helpfulness to the jury, and potential prejudice. People v. Rector, 248 P.3d 1196 (Colo. 2011). A party raising a challenge under Shreck to the admissibility of expert testimony must sufficiently identify the testimony or witness being challenged. People v. Rector, 248 P.3d 1196 (Colo. 2011). "Reasonable medical probability" standard should no longer be used. This rule allows the admission of scientific expert testimony when: (1) the scientific principles at issue are reasonably reliable; (2) the witness is qualified to opine on such principles; (3) the testimony is useful to the jury; and (4) the probative value of the evidence outweighs any potential prejudice. An inquiry into whether the expert expresses his or her opinion to the required degree of medical probability is not appropriate. Estate of Ford v. Eicher, 250 P.3d 262 (Colo. 2011). The reliability analysis hinges on whether the scientific principles the expert employed are grounded in the methods and procedures of science. Estate of Ford v. Eicher, 250 P.3d 262 (Colo. 2011). Gatekeeping function to rule out "junk science" only allows court to determine whether an alternative theory is reasonably reliable. The court abuses its discretion when it determines which of two competing medical theories of causation is the more plausible and prevents the expert from offering the other. Estate of Ford v. Eicher, 220 P.3d 939 (Colo. App. 2008), aff'd, 250 P.3d 262 (Colo. 2011). The fact that there is no ethical way to test an alternative medical theory does not preclude the admissibility of testimony but goes to the weight that the jury may assign to it. Estate of Ford v. Eicher, 220 P.3d 939 (Colo. App. 2008), aff'd, 250 P.3d 262 (Colo. 2011). In determining that expert's testimony is unreliable and, therefore, should not be admitted under this rule, it is not enough for a court to conclude that the testimony is "speculative". Instead, the court must consider whether the scientific principles underlying the testimony are reasonably reliable and whether the expert is qualified to opine on such matters. People v. Ramirez, 155 P.3d 371 (Colo. 2007). Statement of opinion in terms indicating a lack of certainty, such as "a possible mechanism" or "a reasonable supposition", do not by themselves render the opinion speculative. Estate of Ford v. Eicher, 220 P.3d 939 (Colo. App. 2008), aff'd, 250 P.3d 262 (Colo. 2011). Trial court did not commit manifest error when it determined that forensic psychologists' testimony related to motivation and behavior of individuals committing sexual homicides, a recognized subspecialty of forensic psychology, was reasonably reliable, that it was helpful to the jury, and that under C.R.E. 403 the probative value of the testimony was substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, waste of time, or needless presentation of the evidence. Masters v. People, 59 P.3d 979 (Colo. 2002). A trial court has the discretion to determine the admissibility of expert evidence and the trial court committed harmless error by refusing to permit an expert witness to testify on behalf of the plaintiff. Simon v. Truck Ins. Exch., 757 P.2d 1123 (Colo. App. 1988). Admissibility of expert evidence must be evaluated in light of its offered purpose on review for potential abuse of discretion, and prosecution's proffered reason for admitting testimony to show the basis of the expert's opinion that a subdural hematoma is only caused by massive, violent force was an undisputed fact that helped the jury understand the facts of the case, and therefore was not an abuse of discretion. People v. Martinez, 74 P.3d 316 (Colo. 2003). But trial court's admission of evidence of accident scenarios without a showing of a link between shaken-impact syndrome and the accident scenarios was error, as C.R.E. 702 's helpfulness standard requires a valid scientific connection, enunciated to the jury. People v. Martinez, 74 P.3d 316 (Colo. 2003). It was reversible error for the court to fail to apply the helpfulness standard of this rule in determining the admissibility of testimony on the reliability of eyewitness identification. Campbell v. People, 814 P.2d 1 (Colo. 1991). When expert testimony unnecessary. Where the trial court is sitting as a finder of fact and is capable of drawing its own inferences from the facts in the record, it need not admit expert testimony on a matter that it is capable of resolving without such testimony. Tri-State Generation & Transmission Co. v. City of Thornton, 647 P.2d 670 (Colo. 1982). Trial court did not abuse its discretion in admitting expert testimony where defendant did not present any evidence rebutting the reliability or general acceptance of the evidence. Stoczynski v. Livermore, 782 P.2d 834 (Colo. App. 1989). The basis for admissibility under this rule is not that the witness possesses skill in a particular field but that the witness can offer assistance on a matter not within the knowledge or common experience of people of ordinary intelligence. Scognamillo v. Olsen, 795 P.2d 1357 (Colo. App. 1990); Hines v. D. & R.G.W. R. Co., 829 P.2d 419 (Colo. App. 1991). The fact that a witness gained specialized knowledge while working under the supervision of others does not render the witness unqualified. Town of Red Cliff v. Reider, 851 P.2d 282 (Colo. App. 1993). Expert testimony by an architect not licensed in the state may be properly admitted if the trial court determines whether the individual's education, training, experience, and knowledge in the field of architecture establishes that he has special knowledge concerning the architectural standards, including statewide standards applicable to Colorado practitioners, and whether the testimony would aid the court. Corcoran v. Sanner, 854 P.2d 1376 (Colo. App. 1993). Competence to testify as to medical standards. Generally, practitioners of one school of medicine are not competent to testify as experts relative to standards of care required of practitioners of another school. Greene v. Thomas, 662 P.2d 491 (Colo. App. 1982). However, a physician from one specialty may testify concerning the standard of care required of a physician with a different specialty, provided that the expert witness has acquired, through experience or study, more than just a casual familiarity with the standards of care of the defendant's specialty. Greene v. Thomas, 662 P.2d 491 (Colo. App. 1982); Connelly v. Kortz, 689 P.2d 728 (Colo. App. 1984). Where the witness and the defendant are both doctors of podiatric medicine, the testimony is admissible regardless of the difference of the practices. Durkee v. Oliver, 714 P.2d 1330 (Colo. App. 1986). A physician may be qualified as an "expert in medicine" rather than a specialty so long as his or her knowledge, skill, experience, training, or education supports the qualification, and he or she is capable of providing specialized knowledge that will assist the decision-maker in determining the issues. People ex rel. Strodtman, __ P.3d __ (Colo. App. 2011). The test developed in Frye v. United States is applicable to novel scientific devices or processes involving the evaluation of physical evidence. The test contained in this rule is applicable if the evidence is of a general nature and the expert's testimony does not concern this particular victim. Fishback v. People, 851 P.2d 884 (Colo. 1993) (disapproved in People v. Shreck, 22 P.3d 68 (Colo. 2001)). The test developed in Frye v. United States is applicable to the admission of novel scientific evidence. Tran v. Hilburn, 948 P.2d 52 (Colo. App. 1997), overruled by implication in People v. Shreck, 22 P.3d 68 (Colo. 2001). Frye test has not been abandoned in Colorado as an exclusive test of admissibility of certain expert testimony, but its application remains very narrow. Schultz v. Wells, 13 P.3d 846 (Colo. App. 2000). Frye test may be used only if proffered scientific evidence is based on novel scientific devices and processes involving the evaluation of physical evidence. People v. Perryman, 859 P.2d 263 (Colo. App. 1993); Schultz v. Wells, 13 P.3d 846 (Colo. App. 2000). The test established in Frye v. United States requires a showing of (1) general acceptance in the relevant scientific community of the underlying theory or principle, and (2) general acceptance in the relevant scientific community of the techniques used to apply that theory or principle. Fishback v. People, 851 P.2d 884 (Colo. 1993); Tran v. Hilburn, 948 P.2d 52 (Colo. App. 1997); Schultz v. Wells, 13 P.3d 846 (Colo. App. 2000). In evaluating novel scientific evidence under the Frye test, a court must identify the scientific theory, techniques used, and relevant scientific community at issue and then consider the evidence presented at trial, scientific literature on the state of the science in question, and rulings from other jurisdictions employing the same admissibility questions. Tran v. Hilburn, 948 P.2d 52 (Colo. App. 1997). Test for admissibility of expert testimony that does not deal with scientific devices or processes is whether the testimony will assist the trier of fact to understand the evidence or fact in issue. Colwell v. Mentzer Invs., Inc., 973 P.2d 631 (Colo. App. 1998). To determine the admissibility of this type of testimony, the court must hold an in limine proceeding to balance the reliability of the scientific principles upon which the testimony rests with the likelihood that the testimony may overwhelm or mislead the jury. Colwell v. Mentzer Invs., Inc., 973 P.2d 631 (Colo. App. 1998). Applying this test, the court did not abuse its discretion in admitting testimony concerning the effect of stress on causing multiple sclerosis to become symptomatic. Colwell v. Mentzer Invs., Inc., 973 P.2d 631 (Colo. App. 1998). Neither of the tests established in Frye v. United States or Daubert v. Merrell Dow Pharmaceuticals is applicable to dog-tracking evidence because it does not depend upon any scientific device, method, or process. People v. Brooks, 950 P.2d 649 (Colo. App. 1997), aff'd, 975 P.2d 1105 (Colo. 1999). Instead, such evidence concerns a subject of common knowledge: Some dogs can track. While specialized knowledge is involved, the reliability of a particular track is typically demonstrated by evidence that is easily understood by a jury such as the handler's experience, knowledge, and training. People v. Brooks, 950 P.2d 649 (Colo. App. 1997), aff'd, 975 P.2d 1105 (Colo. 1999). Elements of a proper foundation for dog tracking evidence listed in Brooks v. People, 975 P.2d 1105 (Colo. 1999). Harmless error to admit dog tracking evidence, despite improper foundation, where dog handler later testified she and the dog had worked together for five years and performed numerous narcotics sniffs, and that the dog had never alerted officers about money determined to be clean. People v. Martinez, 51 P.3d 1029 (Colo. App. 2001), aff'd in part and rev'd in part on other grounds, 69 P.3d 1029 (Colo. 2003). Frye test does not apply to shoe print identification. The expert's comparative process involves no "manipulation" of evidence, and an understanding of the techniques used is readily accessible to the jury. People v. Perryman, 859 P.2d 263 (Colo. App. 1993); People v. Fears, 962 P.2d 272 (Colo. App. 1997). Frye test should not have been used to exclude evidence related to the results of automobile collision experiments with human volunteers as the tests did not involve a novel scientific process or device applied to the manipulation of physical evidence, but exclusion was nonetheless proper as the trial court did not rely exclusively on the Frye test but also applied C.R.E. 402 and this rule. Schultz v. Wells, 13 P.3d 846 (Colo. App. 2000). Concerns which may arise in the implementation of otherwise generally accepted techniques go to the weight to be accorded to scientific or technical evidence and not to the admissibility of such evidence. Fishback v. People, 851 P.2d 884 (Colo. 1993). Evidence derived from multiplex DNA testing systems was admissible under this rule based on the supreme court findings that multiplex systems are generally reliable, questions as to the reliability of a specific type of multiplex system go to the weight of the evidence, and the specific multiplex systems used in this case had been deemed reliable by other courts. Further, the court found that the probative value of the evidence was not substantially outweighed by the danger of unfair prejudice, confusion, delay, waste of time, or needless presentation of cumulative evidence under C.R.E. 403. People v. Shreck, 22 P.3d 68 (Colo. 2001); People v. Lehmkuhl, 117 P.3d 98 (Colo. App. 2004). Quantitative electroencephalogram (QEEG), which is a computer enhanced electroencephalogram that compares a patient's brain activity with the activity of normally functioning brains, is not generally accepted in the community of clinicians who treat brain injured patients and QEEG evidence is thus not admissible. Tran v. Hilburn, 948 P.2d 52 (Colo. App. 1997). But videofluoroscopy (VF), which is a videotaped x-ray motion picture of a patient's bones and soft tissue structures in motion, is generally accepted by the relevant community of chiropractic professionals and VF evidence is thus admissible. Tran v. Hilburn, 948 P.2d 52 (Colo. App. 1997). The water court properly excluded results derived from surface and ground water models because of a lack of reliability caused by a variety of technical failures by the expert witnesses. In re Water Rights of Park County Sportsmen's Ranch, 105 P.3d 595 (Colo. 2005). Exclusion of testimony held abuse of discretion where oral surgeon had testified as to standard of care for general dentist after the trial court had accepted the witness as an expert in both fields, neither the defendant nor the court had objected to the surgeon's qualification as an expert witness at the time of his testimony, and surgeon had testified that the standard of care for extraction of tooth would be the same for both practitioners. Surgeon's statement, in response to questioning of court, that he could not testify to the overall standard of care for general dentists goes to the weight to be accorded to testimony rather than to its admissibility. Sanchez v. Lauffenburger, 784 P.2d 855 (Colo. App. 1989). Attorneys may testify as experts with respect to insurance industry standards. Klein v. State Farm Mut. Auto. Ins. Co., 948 P.2d 43 (Colo. App. 1997). CPA qualified as expert in accounting. A trial court has discretion in determining the qualifications of an expert and the admissibility of expert evidence. That discretion is properly exercised where a certified public accountant is properly qualified as an expert in accounting and he testifies only regarding his professional opinions as a CPA which have to be made by him in the performance of his duties. Andrikopoulos v. Broadmoor Mgt. Co., 670 P.2d 435 (Colo. App. 1983). Police officers employed in crime lab may testify as experts. A trial court does not abuse its discretion in allowing police officers employed in the crime laboratory to testify as experts when the technicians have qualifications as experts based on technical training and pretrial experience, and the jury is adequately instructed on the weight to be given expert testimony and opinion evidence. People v. Hankin, 179 Colo. 70, 498 P.2d 1116 (1972). There is no requirement that a forensic chemistry expert follow a "written analytical method" before his or her expert testimony may be admitted. Based on the totality of the circumstances, the trial court did not abuse its discretion in admitting the expert testimony without a "written analytical method". People v. Laurent, 194 P.3d 1053 (Colo. App. 2008). Testimony concerning Mexican culture did not constitute specialized knowledge that would assist the trier of fact, and exclusion of proffered expert testimony did not deprive defendant of his constitutional right to present a defense. People v. Salcedo, 985 P.2d 7 (Colo. App. 1998), rev'd on other grounds, 999 P.2d 833 (Colo. 2000). Fact that witness not college graduate does not preclude his testifying as expert. The fact that a police officer is not a college graduate does not preclude his testifying as an expert on the basis of other technical training and pretrial experience. White v. People, 175 Colo. 119, 486 P.2d 4 (1971). Error not found in allowing handwriting expert to testify. People v. Drumright, 181 Colo. 137, 507 P.2d 1097 (1973). Jury is not bound by the testimony of expert witnesses, which must be considered and weighed as that of other witnesses. People v. King, 181 Colo. 439, 510 P.2d 333 (1973). A medical opinion is admissible if founded on reasonable medical probability. Thirsk v. Ethicon, Inc., 687 P.2d 1315 (Colo. App. 1983). These rules, not the standard of "reasonable medical probability", govern the admissibility of expert testimony. To the extent earlier cases approve of this standard, they are overruled. People v. Ramirez, 155 P.3d 371 (Colo. 2007). Internist not allowed to testify regarding the practice of surgeons. Trial court did not abuse its discretion in refusing to allow internist to testify to the standards of practice of surgeons in the Denver metropolitan area when proponent failed to demonstrate that the standards of care in the two fields are in fact similar, and there was testimony that the standards of practice concerning the need for surgery followed by surgeons differ from the standards of practice followed by internists. Connelly v. Kortz, 689 P.2d 728 (Colo. App. 1984). Dispositive consideration in ruling on admissibility of medical witness' expert testimony regarding whether the defendant, who practices in another school of medicine, has adhered to or deviated from the requisite standard of care should be (1)whether the expert is, by reason of knowledge, skill, experience, training, or education, so substantially familiar with the standard or care applicable to the defendant's specialty as to render the witness' opinion testimony as well-informed as would be the opinion of an expert witness practicing the same specialty as the defendant, or (2)whether the standard of care for the condition in question is substantially identical for both specialties. Melville v. Southward, 791 P.2d 383 (Colo. 1990). Expert's testimony of personal practices may be admissible if an expert testified concerning the applicable standard of care because (1) expert's personal practices may help jurors understand why that standard of care is followed; (2) testimony regarding personal practices may either bolster or impeach the credibility of the expert; and, (3) each expert addressed the applicable standard of care. Wallbank v. Rothenberg, 74 P.3d 413 (Colo. App. 2003). Testimony of orthopedic surgeon should not have been admitted on the issue of podiatrist's alleged negligence. The plaintiff failed to establish that the orthopedic surgeon was so substantially familiar with the standard of care for podiatric surgery as to render his opinion testimony as well-informed as that of a podiatrist and failed to establish that the standard of care for the surgery was substantially identical for both the practice of orthopedic surgery and podiatry. Melville v. Southward, 791 P.2d 383 (Colo. 1990). Neuropsychologists are not per se unqualified to speak on the causation of organic brain injury, but a court must satisfy the two-part approach to questions arising under this rule. Huntoon v. TCI Cablevision of Colo., 969 P.2d 681 (Colo. 1998). Trial court did not err when it permitted a physician accepted as an expert in plastic and reconstructive surgery and the care of burn patients to testify that he had discontinued a steroid treatment after burn victim reported gynecological symptoms where physician was not offering an expert opinion on gynecological and obstetrical medicine but rather was giving the reasons for his course of treatment, which were based on the burn victim's physical response to the treatment. Simon v. Coppola, 872 P.2d 10 (Colo. App. 1993). In a trial for sexual assault on a child, the trial court did not err in admitting testimony by the child's therapist, a social worker, about the characteristics present in sexually abused children, the presence of similar characteristics in the child, and the purpose of therapy since such testimony does not rise to the level of an improper assertion that the child was telling the truth and the testimony would assist the jury in determining a fact in issue. People v. Cordova, 854 P.2d 1337 (Colo. App. 1992). In a first-degree sexual assault trial, testimony of counselor consisting of general comments based on her observations of victim's demeanor following alleged sexual assault was not inadmissible as amounting to a scientific diagnosis of rape trauma syndrome, as long as counselor did not use scientific terminology, discuss theory, or state an opinion as to whether she believed victim. People v. Farley, 712 P.2d 1116 (Colo. App. 1985), aff'd, 746 P.2d 956 (Colo. 1987). The trial court did not err by allowing expert testimony in sexual assault case because the lay notion of what behavior follows being raped may not be consistent with the behavior that social scientists have found. This satisfies the test that expert testimony be helpful to the jury. Further, rape trauma syndrome evidence has repeatedly been held to be reliable. People v. Baenziger, 97 P.3d 271 (Colo. App. 2004). Denial of effective counsel. Admission of testimony of defense-retained handwriting expert called by prosecution constitutes denial of effective assistance of counsel. Perez v. People, 745 P.2d 650 (Colo. 1987). Expert witness evidence not admissible. Where expert witness' opinion evidence would not assist the trier of fact in understanding the evidence and where evidence is not of a technical or complex nature, expert testimony is not admissible under this rule. People v. Snook, 729 P.2d 1026 (Colo. App. 1986), aff'd, 745 P.2d 647 (Colo. 1987). This rule was not intended to allow expert testimony on the issue of whether a witness is telling the truth. People v. Snook, 729 P.2d 1026 (Colo. App. 1986), aff'd, 745 P.2d 647 (Colo. 1987). Court properly excluded defendant's expert heat of passion testimony because the heat of passion mitigator does not apply when a person seeks out the highly provoking act in question, as defendant did here. Therefore, trial court properly excluded the testimony since it would not have been helpful to the jury. People v. Valdez, 183 P.3d 720 (Colo. App. 2008). Expert's testimony that victim's statements are consistent with the medical diagnosis do not constitute a subjective opinion concerning the veracity of victim's statements, therefore the testimony may be properly admitted. People v. Wittrein, 198 P.3d 1237 (Colo. App. 2008), rev'd on other grounds, 221 P.3d 1076 (Colo. 2009). Doctor's testimony that she could not imagine that victim's story was fabricated was improper since it was an opinion that victim was telling the truth. People v. Wittrein, 198 P.3d 1237 (Colo. App. 2008), aff'd, 221 P.3d 1076 (Colo. 2009). However, the error was invited by defense counsel's questioning, so reversal is not required. People v. Wittrein, 221 P.3d 1076 (Colo. 2009). While expert opinion on whether children generally have the sophistication to lie about having experienced a sexual assault is admissible, neither a lay nor expert witness may give opinion testimony with respect to whether a witness is telling the truth on a specific occasion. Such testimony invades the province of the jury with respect to its determination of credibility. People v. Higa, 735 P.2d 203 (Colo. App. 1987). Expert testimony on "rape trauma syndrome" admissable on issue of victim's delay in reporting sexual assault where testimony concerned only existence of syndrome and did not involve specific diagnosis of victim. People v. Hampton, 746 P.2d 947 (Colo. 1987). Defense may present expert testimony as to defendant's state of mind in order to bolster a claim of self defense in a homicide case. People v. Young, 825 P.2d 1004 (Colo. App. 1991). Expert testimony on posttraumatic syndrome admissible on issue of child victim's delay in reporting sexual assault, where testimony of expert did not address opinion as to truthfulness of child's statements. People v. Fasy, 829 P.2d 1314 (Colo. 1992). Expert's testimony was properly received to aid the jury in understanding the typicality of reactions by young boys who have been subjected to sexual abuse. Here expert's testimony had been general and she had emphasized that none of her testimony was to be taken as an endorsement of the credibility of any individual. People v. Morrison, 985 P.2d 1 (Colo. App. 1999), aff'd on other grounds, 19 P.3d 668 (Colo. 2000); People v. Mintz, 165 P.3d 829 (Colo. App. 2007). Trial court did not abuse its discretion by finding that an expert's explanation of possible child behaviors and reactions would be helpful to the trier of fact and was admissible. People v. Whitman, 205 P.3d 371 (Colo. App. 2007). Admissibility of expert testimony based on results of absorption inhibition testing in rape case. Since the absorption inhibition method has been recognized as based upon accepted scientific principles, trial court admission of such evidence based upon an offer of proof was a proper exercise of discretion. People v. Banks, 804 P.2d 203 (Colo. App. 1990). Testimony by voice-print expert is not sufficiently reliable to be admissible. People v. Drake, 748 P.2d 1237 (Colo. 1988). Investigating police officer determined to be expert. An investigating police officer may give expert opinion if the subject is complex, is susceptible to opinion evidence, and the witness is qualified to give an opinion. Eggert v. Mosler Safe Co., 730 P.2d 895 (Colo. App. 1986). Trial court did not err in refusing to permit expert testimony on the factors affecting the reliability of eyewitness identification. People v. Beaver, 725 P.2d 96 (Colo. App. 1986). Expert testimony on the reliability of eyewitness identification is not per se admissible. Rather, admissibility of such evidence is left to the trial court's discretion. The trial judge must consider both this rule and C.R.E. 403 in determining the admissibility of such evidence and such determination may not be reversed unless it is manifestly erroneous. Campbell v. People, 814 P.2d 1 (Colo. 1991). Trial court did not err in admitting results of a defendant's breath-alcohol test and allowing expert witness to testify about alcohol's effect on a person's inhibitions. People v. Covington, 988 P.2d 657 (Colo. App. 1999), rev'd on other grounds, 19 P.3d 15 (Colo. 2001). The trial court has broad discretion to evaluate on a case by case basis whether expert testimony on the issue would assist the trier of fact to understand evidence or to determine facts in issue. The appellate court will not reverse the trial court's ruling to admit or exclude such expert testimony unless the ruling is manifestly erroneous. People v. Kemp, 885 P.2d 260 (Colo. App. 1994). Admissibility of experience-based specialized knowledge that is not dependent on a scientific explanation depends on whether the evidence is reasonably reliable information that will assist the trier of fact, which question requires the court to find that the testimony on the subject would be useful to the jury and that the witness is qualified to render an opinion on the subject. Brooks v. People, 975 P.2d 1105 (Colo. 1999); Salcedo v. People, 999 P.2d 833 (Colo. 2000). Trial court erred in excluding expert testimony on reliability of eyewitness identification where eyewitness identification of defendant was the only substantial element of the prosecution's case, eyewitnesses expressed high confidence in their identification of defendant, and proffered expert testimony would have shown a poor relationship between the confidence of eyewitnesses, in general, and the reliability of such witnesses' testimony. People v. Campbell, 847 P.2d 228 (Colo. App. 1992). Three-part test under equivalent federal rule applied in People v. Campbell, 847 P.2d 228 (Colo. App. 1992). Where challenged testimony addressed a collection of behaviors which are typical of children who have been sexually abused, the fact that some of these behaviors were observed as occurring in the victim serves the proper purposes of corroborating the testimony of the victim and does not make such testimony inadmissible. The testimony of the dynamics of child sexual assault could be used by the jury to understand the evidence and determine facts in issue and was properly admitted. People v. Woertman, 786 P.2d 443 (Colo. App. 1989). Expert testimony concerning drug courier profile was not properly admitted because it was not helpful to the jury since it was inherently subjective, of dubious reliability, and logically irrelevant, and because its probative value was substantially outweighed by a risk of misleading the jury. Salcedo v. People, 999 P.2d 833 (Colo. 2000). Present or former employees of the insurance industry are not the only persons qualified to render expert opinions about its operation. Attorneys with extensive experience in workers' compensation who have dealt extensively with defendant and other insurance companies may testify as experts regarding the standard of good faith conduct of an insurer. Southerland v. Argonaut Ins. Co., 794 P.2d 1102 (Colo. App. 1990). Trial court did not abuse discretion by not accepting a convict to testify as an expert witness in parole procedures. Cardiel v. Brittian, 833 P.2d 748 (Colo. 1992). District court did not abuse discretion in denying habeas corpus petitioner proffered expert witness. Although witness, a fellow inmate of the petitioner, had some training and experience with habeas corpus petitions and other parole issues, trial court cannot be found to have abused its discretion in refusing to accept the witness as an expert in administrative procedures concerning parole. Cardiel v. Brittian, 833 P.2d 748 (Colo. 1992). This rule contained the appropriate test to determine the admissibility of expert testimony when the process used by the expert involved no manipulation of physical evide8041nce and the understanding of the expert's techniques was readily accessible to the jury. The expert's testimony compared the characteristics of defendant's shoes with prints found near the victim's body. People v. Perryman, 859 P.2d 263 (Colo. App. 1993). A court may rely on the testimony of a single witness in admitting scientific evidence under Frye if the witness is qualified to render an opinion as to the general acceptance of the techniques and the opposing party has the opportunity to cross-examine the expert. People v. Perryman, 859 P.2d 263 (Colo. App. 1993). Where expert witness had 16 years' experience, was familiar with literature in the field, and had testified as an expert in numerous prior cases the court could rely on such expert's testimony without additional, independent expert testimony. People v. Perryman, 859 P.2d 263 (Colo. App. 1993). Court did not abuse its discretion in deeming witness qualified to testify as an expert given witness's extensive experience, knowledge, and training. People v. Rojas, 181 P.3d 1216 (Colo. App. 2008). Where expert's opinion is based upon reliable data, including unrebutted published studies and the treatment of at least 50 patients with exposure to the same toxic substance as that to which plaintiff was exposed, there was no error in admitting testimony regarding causation, as it is both helpful and competent. Salazar v. Am. Sterlizer Co., 5 P.3d 357 (Colo. App. 2000). Court did not abuse its discretion in concluding that a witness who was not a real estate appraiser could offer testimony concerning property values. The court was satisfied that the extent of the witness's training and experience qualified him to express an expert opinion regarding the effect of environmental contamination on property values even though he was not a real estate appraiser. Antolovich v. Brown Group Retail, Inc., 183 P.3d 582 (Colo. App. 2007). Where substantial expert testimony concerning DNA testing supported admissibility of DNA evidence, it was within the trial court's discretion to allow consideration of the evidence. People v. Lindsey, 868 P.2d 1085 (Colo. App. 1993). Trial court did not err in admitting DNA evidence where DNA expert could not definitely identify victim as a contributor of the DNA. Testimony was relevant in that it showed it was more probable than not that victim contributed to the DNA. People v. Rojas, 181 P.3d 1216 (Colo. App. 2008). Although an expert witness should not dictate the law that a jury should apply, an expert witness is permitted, in the trial court's discretion, to refer to the facts of a case in legal terms. Thus, expert's testimony was admissible insofar as it concerned party's contention that insurer's conduct constituted bad faith based on purported violations of the Unfair Claims Settlement Practices Act. Such testimony was helpful as it served to explain complex issues of insurance company claims management practices. Peiffer v. State Farm Mut. Auto. Ins., 940 P.2d 967 (Colo. App. 1996), aff'd on other grounds, 955 P.2d 1008 (Colo. 1998). Any legal conclusions tendered by witness were elicited during her cross-examination by defendant's counsel, and thus, any error regarding witness's testimony was injected at defendant's behest. Such error cannot serve as grounds for reversal on appeal by defendant. Bd. of Comm'rs v. Fixed Base Operators, 939 P.2d 464 (Colo. App. 1997). No abuse of discretion for trial court to permit expert testimony regarding the steps a reasonably prudent applicant in a Torrens action would take to ascertain the names of persons who claimed an interest in the property and to rely on that testimony in reaching its conclusions on due process issues. Lobato v. Taylor, 13 P.3d 821 (Colo. App. 2000), rev'd on other grounds, 71 P.3d 938 (Colo. 2002). Expert testimony concerning reasons for victims' recantations is admissible in cases involving domestic violence. People v. Johnson, 74 P.3d 349 (Colo. App. 2002); People v. Wallin, 167 P.3d 183 (Colo. App. 2007). Trial court properly excluded expert witness's testimony as unnecessary and as improperly usurping the court's function because: (1) The testimony was not needed to describe or interpret the crime setting; (2) the testimony was not a question for the jury; (3) the testimony would not have assisted the trier of fact; and (4) an expert testifying as to issues of law may not simply tell the jury what result to reach. People v. Lesslie, 939 P.2d 443 (Colo. App. 1996). Prosecutor's use of expert testimony regarding drug courier profiles as substantive evidence of defendant's guilt was improper, and, although a reasonable jury could have convicted on other evidence, the admissible evidence did not overwhelmingly establish defendant's guilt, and there is a significant probability that the erroneously admitted testimony substantially influenced the jury's verdict, and thus was not harmless. Salcedo v. People, 999 P.2d 833 (Colo. 2000). Court abused its discretion in admitting some lay opinions from mental health providers who had not been properly noticed as experts by the prosecution. Some of the opinions were expert opinions improperly admitted under the guise of lay opinion testimony. The improper testimony related to symptoms of specific mental illness and opinions about whether defendant suffered from mental illness. The evidence relied upon the witness' specialized knowledge and training and, therefore, went beyond the bounds of lay opinion. The error in this case was harmless since there was ample evidence in addition to the improperly admitted opinions. Dunlap v. People, 173 P.3d 1054 (Colo. 2007), cert. denied, 552 U.S. 1105, 128 S. Ct. 882, 169 L. Ed. 2d 740 (2008). Mathematical probability statements or numerical conclusions by an expert witness on ergonomics properly excluded if (1) the conclusion was without statistical support in the record and (2) such a statement or conclusion implied a non-purposeful or non-intentional state of mind by the defendant and the expert was not qualified to testify regarding the defendant's psychological condition. People v. Wilkerson, 114 P.3d 874 (Colo. 2005). Allowing police officer's testimony regarding the use of glass pipe and torch lighter to smoke methamphetamine not plain error. People v. Malloy, 178 P.3d 1283 (Colo. App. 2008). Trial court improperly limited testimony of defendant's expert witness after prosecution had opened the door to this testimony and error was not harmless beyond a reasonable doubt. Golob v. People, 180 P.3d 1006 (Colo. 2008). Applied in People in Interest of K.A.J., 635 P.2d 921 (Colo. App. 1981); People v. Ortega, 672 P.2d 215 (Colo. App. 1983); People v. Jones, 743 P.2d 44 (Colo. App. 1987); People v. Williams, 761 P.2d 258 (Colo. App. 1988); People v. Groves, 854 P.2d 1310 (Colo. App. 1992); People v. Masters, 33 P.3d 1191 (Colo. App. 2001), aff'd, 59 P.3d 979 (Colo. 2002); People v. Martinez, 51 P.3d 1029 (Colo. App. 2001), aff'd in part and rev'd in part on other grounds, 69 P.3d 1029 (Colo. 2003); Luster v. Brinkman, 205 P.3d 410 (Colo. App. 2008).