Conn. R. Evid. 7-2
A witness qualified as an expert by knowledge, skill, experience, training, education or otherwise may testify in the form of an opinion or otherwise concerning scientific, technical or other specialized knowledge, if the testimony will assist the trier of fact in understanding the evidence or in determining a fact in issue.
Conn. Code. Evid. 7-2
COMMENTARY
The subject matter upon which expert witnesses may testify is not limited to the scientific or technical fields, but extends to all areas of specialized knowledge. See State v. Edwards, 325 Conn. 97, 127-28, 156 A.3d 506 (2017) (explaining what qualifies as expert testimony); see, e.g., State v. Correa, 241 Conn. 322, 355, 696 A.2d 944 (1997) (FBI agent permitted to testify about local cocaine distribution and its connection with violence); State v. Hasan, 205 Conn. 485, 494 -95, 534 A.2d 877 (1987) (podiatrist permitted to testify about physical match between shoe and defendant's foot).
Section 7-2 requires a party offering expert testimony, in any form, to show that the witness is qualified and that the testimony will be of assistance to the trier of fact. A three-part test is used to determine whether these requirements are met. See, e.g., Sullivan v. Metro- North Commuter R. Co., 292 Conn. 150, 158-59, 971 A.2d 676 (2009). First, the expert must possess knowledge, skill, experience, training, education or some other source of learning directly applicable to a matter in issue. See, e.g., Weaver v. McKnight, 313 Conn. 393, 406-409, 97 A.3d 920 (2014); State v. Borrelli, 227 Conn. 153, 166-67, 629 A.2d 1105 (1993), State v. Girolamo, 197 Conn. 201, 214-15, 496 A.2d 948 (1985). Second, the witness' skill or knowledge must not be common to the average person. See, e.g., State v. Guilbert, 306 Conn. 218, 234-42, 49 A.3d 705 (2012); State v. Borrelli, supra, 167-172. Third, the testimony must be helpful to the fact finder in considering the issues. See, e.g., State v. Hasan, supra, 205 Conn. 494 ("[t]he value of [the witness'] expertise lay in its assistance to the jury in reviewing and evaluating the evidence''). The inquiry is often summarized in the following terms: "The true test of the admissibility of [expert] testimony is not whether the subject matter is common or uncommon, or whether many persons or few have some knowledge of the matter; but it is whether the witnesses offered as experts have any peculiar knowledge or experience, not common to the world, which renders their opinions founded on such knowledge or experience any aid to the court or jury in determining the questions at issue.'' (Internal quotation marks omitted.) Going v. Pagani, 172 Conn. 29, 35, 372 A.2d 516 (1976).
The case law imposes an additional admissibility requirement with respect to some but not all types of scientific expert testimony. This additional requirement derives from State v. Porter, 241 Conn. 57, 698 A.2d 739 (1997), cert. denied, 523 U.S. 1058, 118 S. Ct. 1384, 140 L. Ed. 2d 645 (1998), which directs trial judges, in considering the admission of certain types of scientific expert testimony, to serve a gatekeeper function in determining whether such evidence will assist the trier of fact. Id., 73. Porter adopted an approach similar to that taken by the United States Supreme Court in construing the analogous federal rule of evidence in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125 L. Ed. 2d 469 (1993). State v. Porter, supra, 61, 68. For scientific expert testimony subject to Porter, the three-part test discussed above is supplemented by a fourth threshold requirement. Id., 81; see Maher v. Quest Diagnostics, Inc., 269 Conn. 154, 168, 847 A.2d 978 (2004); Weaver v. McKnight, supra, 313 Conn. 414-15. This fourth requirement itself has two parts. State v. Porter, supra, 63-64; see, e.g., Weaver v. McKnight, supra, 413-14. The proffering party first must establish that the scientific expert testimony is reliable. State v. Porter, supra, 64. Scientific expert testimony is reliable if the underlying reasoning or methodology is scientifically valid. Id. The Porter decision identifies several factors that should be considered by a trial judge to help decide whether scientific expert testimony is reliable. Id., 84-86. This list of factors is not exclusive; id., 84; and the operation of each factor varies depending on the specific context in each case. Id., 86-87. The second part of the Porter analysis requires the trial judge to determine that the proffered scientific evidence is relevant to the case at hand, meaning that the reasoning or methodology underlying the scientific theory or technique in question properly can be applied to the facts in issue. Id. "In other words, proposed scientific testimony must be demonstrably relevant to the facts of the particular case in which it is offered, and not simply valid in the abstract.'' Id., 65; see Weaver v. McKnight, supra, 414. This is sometimes called the "fit requirement'' of Porter. State v. Guilbert, supra, 306 Conn. 232; see State v. Porter, supra, 83. The relevance and prejudice analysis under Article IV of the Code also remains fully applicable to scientific expert testimony. See State v. Kelly, 256 Conn. 23, 74-76, 770 A.2d 908 (2001).
The Porter analysis applies only to certain types of scientific expert testimony. State v. Reid, 254 Conn. 540, 546, 757 A.2d 482 (2000); see Maher v. Quest Diagnostics, Inc., supra, 269 Conn. 170 n.22 ("certain types of evidence, although ostensibly rooted in scientific principles and presented by expert witnesses with scientific training, are not `scientific' for the purposes of our admissibility standard for scientific evidence, either before or after Porter''). The cases have articulated two categories of scientific expert testimony that are not subject to the additional analysis required under Porter. The first category reflects the fact that "some scientific principles have become so well established [in the scientific community] that an explicit Daubert analysis is not necessary for admission of evidence thereunder.'' State v. Porter, supra, 241 Conn. 85 n.30 ("a very few scientific principles are so firmly established as to have attained the status of scientific law, such as the laws of thermodynamics'' [internal quotation marks omitted]); see State v. Kirsch, 263 Conn. 390, 402-403, 820 A.2d 236 (2003). The second type of scientific expert testimony exempt from the Porter analysis is evidence that leaves the jury "in a position to weigh the probative value of the [expert] testimony without abandoning common sense and sacrificing independent judgment to the expert's assertions based on his special skill or knowledge.'' State v. Hasan, supra, 205 Conn. 491; see State v. Reid, supra, 546-47. This exception recognizes that certain expert testimony, though scientific in nature, may be presented in a manner, or involve a subject matter, such that its admission does not risk supplanting the role of "lay jurors awed by an aura of mystic infallibility surrounding scientific techniques, experts and the fancy devices employed.'' (Internal quotation marks omitted.) State v. Hasan, supra, 490.
The United States Supreme Court has held that the trial judge's gatekeeping function under Fed. R. Evid. 702 applies not only to testimony based on scientific knowledge, but also to testimony based on technical and other specialized knowledge, and that the trial judge may consider one or more of the Daubert factors if doing so will aid in determining the reliability of the testimony. Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 147-49, 119 S. Ct. 1167, 143 L. Ed. 2d 238 (1999). The Code takes no position on [such] an application of Porter to testimony based on technical and other specialized knowledge. Thus, Section 7-2 should not be read either as including or precluding the Kumho Tire rule. See State v. West, 274 Conn. 605, 638 n.37, 877 A.2d 787, cert. denied, 546 U.S. 1049, 126 S. Ct. 775, 163 L. Ed. 2d 601 (2005) (declining to decide issue).
In cases involving claims of professional negligence or other issues beyond the field of the ordinary knowledge and experience of judges or jurors, expert testimony may be required to establish one or more elements of a claim. See, e.g., Boone v. William W. Backus Hospital, 272 Conn. 551, 567, 864 A.2d 1 (2005) (medical malpractice); Davis v. Margolis, 215 Conn. 408, 415-16, 576 A.2d 489 (1990) (legal malpractice); see Doe v. Hartford Roman Catholic Diocesan Corp., 317 Conn. 357, 377-78, 119 A.2d 462 (2015) (holding that expert testimony not required to assess risk of relapse of alcoholic priest, known to defendant as child molester, whose tendencies were exacerbated by alcohol); LePage v. Home, 262 Conn. 116, 125-26, 809 A.2d 505 (2002) (expert testimony required in case involving consideration of risk factors for sudden infant death syndrome).