Key Concepts

  • Expert testimony regarding various factors that may undermine the accuracy or trustworthiness of a witness’s identification of the defendant as the perpetrator has been admitted into evidence in some cases.
  • The trial court has the discretion to exclude such testimony if the court finds it to be irrelevant, prejudicial, or confusing, or if the expert’s proposed testimony does not satisfy the admissibility requirements of Rule 702(a).


Practice Pointer

Identification, line-ups and show-ups
This entry addresses expert testimony about “eyewitness identification” in general (i.e., the overall accuracy and reliability of an eyewitness’s identification of the defendant). Many of the arguments about errors or limitations with eyewitness identification are specifically referring to situations where an eyewitness has made a positive identification at a line-up or show-up before trial, and the defense intends to argue that the procedure used to conduct that prior identification was unduly suggestive or otherwise flawed.
North Carolina has adopted statutory guidelines for both line-ups and show-ups that include numerous safeguards to ensure that those procedures are conducted in a fair and neutral manner (e.g., directing that a line-up be conducted by an independent actor who is not involved in the investigation, informing the witness before viewing a line-up that the suspect might not be pictured, and requiring that show-ups be done in-person rather than with photos). For more information about these guidelines, see Robert Farb, "North Carolina Statutory Requirements Concerning How to Conduct Lineups and Show-ups," North Carolina Criminal Law Blog, June 12, 2017.


In cases where the state’s evidence includes an eyewitness’s identification of the defendant as the perpetrator, the defense may seek to counter that evidence with expert testimony disputing the accuracy and reliability of eyewitness identifications in general, or identifying factors in the case at hand that call into question the accuracy of the eyewitness’s identification of the defendant. Critics have noted that although eyewitness identification of the defendant as the perpetrator of the crime is usually very important evidence for the state, this type of testimony has been found to be erroneous in some cases, such as where defendants who were convicted based on eyewitness testimony were subsequently exonerated by DNA evidence. See 2 David L. Faigman, et al, Modern Scientific Evidence: The Law and Science of Expert Testimony 578 (2016-17 ed.). The defense may seek to offer expert testimony to help explain how and why such testimony can be wrong, by, for example, describing the impact of “estimator variables” (factors that affect the eyewitness’s ability to perceive and describe the events accurately, such as poor lighting conditions, the distracting presence of a weapon, or the way memories can change over time) and “system variables” (factors such as the suggestiveness of a photo line-up or the improper manner in which a show-up was conducted). Id. For more general background information on factors that can impact the reliability of eyewitness identifications, see the following:

  1. John Bohannon, “How Reliable is Eyewitness Testimony? Scientists Weigh In,” Science, Vol. 361, No. 6400, October 3, 2014;
  2. “The Science Behind Eyewitness Identification Reform,” The Innocence Project,, as viewed on August 2, 2018; and
  3. John Nardizzi, “The Law and Science of Eyewitness Identification,” Pursuit Magazine, June 20, 2017

If the defendant is indigent and requests funds to hire an eyewitness identification expert, the defendant must show the court that “the matter subject to expert testimony is ‘likely to be a significant factor’ in the defense,” and the defendant has a “particularized need” for the expert’s assistance. State v. Abraham, 338 N.C. 315 (1994) (trial court properly denied defendant’s request for appointment of eyewitness identification expert where both defendants were identified by multiple witnesses who personally knew them, other evidence corroborated the identification, and the defendant’s presence at the scene was not a significant issue for trial); State v. Sellars, 52 N.C. App. 380 (1981) (similar ruling).

Practice Pointer

Jury instructions on eyewitness identification?
Some jurisdictions have even allowed the use of special jury instructions that address the possibility of mistaken eyewitness identification, particularly when it concerns cross-racial identification. For a more detailed discussion of this issue, see Alyson Grine, “A New Approach: Instruction on the Decreased Reliability of Cross-Racial Identifications,” North Carolina State Bar Journal, Fall 2018, p. 12.
Prosecutors faced with a similar request from the defense should point out that North Carolina’s existing pattern jury instruction on Witness Credibility, N.C.P.I.-101.15, already instructs jurors to consider “the opportunity of the witness to see, hear, know, or remember the facts or occurrences about which the witness testified.” See State v. Watlington, 234 N.C. App. 580 (2014) (trial court did not abuse its discretion in refusing to give lengthy instruction requested by the defense regarding eyewitness identification issues). The court in Watlington specifically held that “the existing pattern jury instructions governing the manner in which jurors should evaluate the weight and credibility of the evidence and the necessity for the jury to find that the defendant perpetrated the crime charged beyond a reasonable doubt sufficiently address the issues arising from the presentation of eyewitness identification testimony,” and concluded that “we do not believe that the additional instruction that Defendant requested in this case had adequate evidentiary support.” Id.

Admissibility and Reliability

As with any expert testimony, admissibility depends on a fact-specific inquiry into the witness’s qualifications, the reliability of the underlying principles and methods, the application of those principles and methods to the facts of the case, and consideration of whether the testimony is helpful to the finder of fact or unfairly prejudicial. See generally G.S. 8C-1, Rule 702(a); State v. McLean, 183 N.C. App. 429 (2007) (whether to admit expert testimony under these standards is in the trial court’s discretion); see also Moore v. Hardee, 723 F.3d 488 (4th Cir. 2013) (“expert testimony on eyewitness identifications is not automatically admitted; when allowed, its admissibility is generally at the court’s discretion, both under federal and North Carolina law”).

Most of the North Carolina cases on this issue have addressed situations where the trial court excluded the expert’s testimony, and the appellate courts have consistently affirmed the judge’s exercise of discretion on the matter. See, e.g., State v. Richardson, 255 N.C. App. 842 (2013) (unpublished) (in a case where the proposed defense expert on eyewitness identification “did not interview the witnesses and did not hear all of the in-court testimony . . . the trial court did not abuse its discretion by concluding that the testimony would have been unfairly prejudicial and was more prejudicial than probative”).

In general, decisions admitting or excluding expert testimony on this issue tend to fall into one of three categories:

Testimony Excluded: Inadequate Qualifications, Methods, or Data

When the proposed expert witness is not sufficiently qualified to render an opinion, or when that opinion is not based on reliable scientific principles that have been applied to the particular facts of the case, the trial judge may properly exclude the testimony. E.g., State v. McLean, 183 N.C. App. 429 (2007) (trial court did not err by excluding expert testimony on eyewitness identification where the defense expert did not interview the witnesses, visit the crime scene, or listen to court testimony); State v. Lee, 154 N.C. App. 410 (2002) (affirming the exclusion of testimony from a proposed expert on eyewitness identification in part because the witness “had not interviewed the victims, did not visit the crime scene, and did not observe any of the eyewitnesses’ testimony at trial” and much of the proposed testimony “was not case specific”); State v. Suddreth, 105 N.C. App. 122 (1992) (trial court did not err in excluding testimony of expert witness proffered by defense concerning factors affecting reliability of eyewitness identification, on grounds that the testimony was not case specific, and expert did not interview victim, visit scene of crime, or observe victim testify, so the only basis for expert’s testimony was his review of a transcript of victim’s testimony); but see State v. Walston, 369 N.C. 547 (2017) (holding that trial court did not abuse its discretion by excluding testimony from a defense expert regarding repressed memory and the suggestibility of memory, but noting that it would not be proper to exclude such testimony solely because the expert has not interviewed or examined the witness: “[s]uch a requirement would create a troubling predicament given that defendants do not have the ability to compel the State’s witnesses to be evaluated by defense experts”).

Testimony Excluded: Irrelevant, Unfairly Prejudicial or Confusing

Even if a witness is properly qualified and has applied reliable scientific principles to the facts of the case, the trial judge still has discretion to exclude the proposed testimony if he or she finds that it is irrelevant, unfairly prejudicial, or needlessly confusing for the jury. See, e.g., State v. McLean, 183 N.C. App. 429 (2007) (no abuse of discretion where the trial court found that, in addition to being insufficiently based on the facts of the case, the value of the proposed expert testimony on eyewitness identification was “marginally weak” and would be confusing, unhelpful to the jury, and unnecessarily delay the proceeding); State v. Knox, 78 N.C. App. 493 (1985) (affirming trial court’s exclusion of expert testimony from “a professor of psychology . . . [concerning] memory variables affecting eyewitness identification” on the grounds that the evidence was “not of sufficient probative value and would serve only to confuse the jury,” especially given that the witness had not interviewed the victim who made the identification – the court of appeals affirmed, and noted that the proposed testimony was also general in nature and the witness did not apply the “memory variables” to “the facts of this case,” thereby limiting the probative value of the testimony); see also State v. Richardson, 255 N.C. App. 842 (2013) (unpublished) (trial court did not abuse its discretion in excluding expert testimony on eyewitness identification where expert “did not hear the testimony of the defense witnesses, [so] she would have only testified about the reliability of the State's witnesses' identification. Therefore, the trial court did not abuse its discretion by concluding that the testimony would have been unfairly prejudicial and was more prejudicial than probative.”).

Testimony Admitted: Relevant, Helpful, Adequate Foundation

If the trial court finds that the proposed expert testimony meets the requirements of Daubert and Rule 702 and is not otherwise barred, it may be admitted. See, e.g., State v. Robinson, 330 N.C. 1 (1991) (the trial judge allowed the defendant to call a witness “to attack the weight and credibility of the State’s identification testimony,” and found the witness “to be an expert in the field of clinical psychology with emphasis in the area of perception and eyewitness identification”; the witness testified, among other things, that “whites have a more difficult time identifying blacks than identifying other whites”); see also United States v. Harris, 995 F.2d 532 (4th Cir. 1993) (summarizing that “[u]ntil fairly recently, most, if not all, courts excluded expert psychological testimony on the validity of eyewitness identification” but that in recent years, courts have recognized that trial courts have the discretion to allow such testimony under certain circumstances, such as when a case involves “cross-racial identification, identification after a long delay, identification after observation under stress,” and the like – however, “[o]utside of such narrowly constrained circumstances, jurors using common sense and their faculties of observation can judge the credibility of an eyewitness identification, especially since deficiencies or inconsistencies in an eyewitness’s testimony can be brought out with skillful cross-examination” and in the case at bar, the circumstances did not warrant the introduction of expert testimony). The United States Supreme Court has also noted that “some States . . . permit defendants to present expert testimony on the hazards of eyewitness identification evidence.” Perry v. New Hampshire, 565 U.S. 228 (2012), quoting State v. Clopten, 223 P.3d 1103 (2009) (“We expect ... that in cases involving eyewitness identification of strangers or near-strangers, trial courts will routinely admit expert testimony [on the dangers of such evidence].”).

Compromise: Partial Admissibility

Even if the trial judge does allow the expert to testify about eyewitness identification, the court can still impose appropriate limits on the scope of the issues that will be addressed and exclude any portions of the witness’s testimony that are deemed inadmissible on other grounds. See State v. Vann, 261 N.C. App. 724 (2018) (affirming trial court's ruling that defense expert could not opine on how the length of the encounter or the presence of a disguise can impact eyewitness identification, since those were common sense factors the jury could assess on its own, but allowing testimony about the potential effects of stress and the presence of a weapon); State v. Robinson, 330 N.C. 1 (1991) (defense eyewitness identification expert was properly prohibited from testifying about the results of a particular experiment on cross-racial misidentification – the witness “never gave a specific opinion concerning the accuracy of eyewitness identification when the actual perpetrator is not in the lineup,” so the results of the experiment were not part of the basis of his opinion under Rule 703 and were therefore inadmissible); see also State v. Ward, 364 N.C. 133, 146 n.5 (2010) (noting the general rule that “[c]aution should be exercised in assuring that the subject matter of the expert witness's testimony relates to the expertise the witness brings to the courtroom”) (internal quotation omitted).

Portions of this entry were excerpted from the North Carolina Superior Court Judges’ Benchbook, “Criminal Evidence: Expert Testimony,” Aug. 2017, Jessica Smith.