From the President: First Convictions Vacated as a Result of the Hair Microscopy Review Project Show

For decades, in the majority of cases involving microscopic hair comparison, FBI experts gave testimony that erroneously stated the significance of the hair comparison results. The fact that convictions have been vacated as a result of the Hair Microscopy Review Project shows the effectiveness of the joint effort among NACDL, the FBI, and the Innocence Project.

Access to The Champion archive is one of many exclusive member benefits. It’s normally restricted to just NACDL members. However, this content, and others like it, is available to everyone in order to educate the public on why criminal justice reform is a necessity.

For decades the FBI laboratory conducted microscopic hair comparison to determine if the characteristics of a known hair sample were consistent with those of an unknown sample for the purpose of providing evidence of identity. The FBI made its services available in state prosecutions, and in many cases examiners from the FBI laboratory testified as to their conclusions concerning the evidentiary weight of their analyses. The problem is that in the overwhelming majority of the cases in which FBI experts testified, they erroneously stated the significance of the results of the hair comparison. The errors have been categorized as follows: (1) stating that the comparison indicated that the known and unknown hair samples came from the same individual; (2) stating that there is a particular degree of probability that the hairs came from the same person, and (3) interjecting the examiner’s great experience with hair comparisons and his perceived historical accuracy to give the impression that he had developed a particular degree of skill enabling him to identify the hairs as having come from the same person.

The problem with this testimony is that no scientific basis exists for it. In 2009, the National Academy of Sciences (NAS) specifically addressed microscopic hair analysis in its groundbreaking report on forensic science.1 The NAS report stated that “[n]o scientifically accepted statistics exist about the frequency with which particular characteristics of hair are distributed in the population. There appear to be no uniform standards on the number of features on which hairs must agree before an examiner may declare a ‘match.’”2 The report further observed that “[there is] no scientific support for the use of hair comparisons for individualization in the absence of nuclear DNA. Microscopy and mtDNA analysis can be used in tandem and may add to one another’s value for classifying a common source, but no studies have been performed specifically to quantify the reliability of their joint use.”3 

Unfortunately, the problems with microscopic hair comparison identified by the NAS report were confirmed as not being merely theoretical. Between 2009 and 2013, DNA testing exonerated three men serving lengthy prison sentences whose convictions rested, at least in part, on microscopic hair analysis evidence that exceeded the proper limits of science. As a result, the FBI began a review of the reports and testimony by its experts on hair microscopic analysis. This led to an historic agreement among the FBI, NACDL, and The Innocence Project (IP) to conduct a review of cases in which the potentially flawed evidence may have played a part in a conviction.4 

In general terms, the agreement called for the FBI to identify cases in which its lab conducted hair microscopic analysis and the result was other than exclusion of the accused (or victim) as the source of the unknown sample. Where testimony was offered by an FBI expert, an effort would be made to locate the transcripts of the testimony to determine if errors had been made. The FBI would review the reports and transcripts and would notify NACDL and IP of its findings concerning whether the reports or testimony was flawed in a given case. The errors in testimony were to be categorized as set forth above. The FBI would then notify NACDL and IP of its conclusions, and lawyers working with NACDL and IP would conduct an independent review of the report and transcripts.5 The FBI would be notified of the results of this review; a procedure was put in place for attempting to reconcile disagreements. If errors were found, notice of the results of the review would be sent to the prosecuting authority that obtained the conviction, NACDL and IP, and the convicted individual would be notified directly or through his attorney.

A fundamental aspect of the review is that the FBI agreed with the other parties as to the proper scientific limits of microscopic hair analysis. It may indicate, at the broad class level, that a contributor of a known sample could be included in a pool of people of unknown size, as a possible source of the sample of unknown origin. It would be improper for this testimony to go into probabilities or any other opinion as to the likelihood of the positive comparison or of the size of the class. It would be proper to state that the comparison excluded an individual as the source of the unknown sample.6 

Because the FBI in 1996 began augmenting its microscopic hair comparisons with DNA testing, the review focuses on cases analyzed prior to Dec. 31, 1999. The results of the review have been startling. A joint press release from NACDL, IP, FBI, and DOJ (issued on April 20, 2015) reported that the error rate found in cases involving testimony by FBI experts was at least 90 percent. It further stated that 26 of 28 FBI experts had provided erroneous testimony concerning hair analysis.7 NACDL Executive Director Norman Reimer was quoted in the press release:

It will be many months before we can know how many people were wrongly convicted based on this flawed evidence, but it seems certain that there will be many whose liberty was deprived and lives destroyed by prosecutorial reliance on this flawed, albeit highly persuasive evidence. Just as we need lawmakers to prevent future systemic failures, we need courts to give those who were impacted by this evidence a second look at their convictions.

On Jan. 26, 2016, a Massachusetts trial court fulfilled the need of which Norman spoke. As a result of the joint FBI, NACDL and IP review project, George Perrot received notice in 2014 that the testimony at his trial of an FBI hair examiner was flawed. A judge granted new trials on a 1992 rape and two burglary convictions because the testimony exceeded the proper limitations of the science.8 A third burglary conviction found to have not been impacted by the testimony was left intact.

The Perrot case and the hair microscopy review process provide a great example of how erroneous forensic science and its potentially horrendous results can be identified and corrected through cooperation between the agencies responsible for the evidence and the defense bar. The FBI identified its flawed practices and moved forward to rectify the situation by agreeing to work together with those with the most skill in analyzing the evidence from the defense perspective. Rather than trying to cover up for the errors or attempting to interfere with the resulting re-examination of affected convictions, the FBI concentrated on the science and worked to get it right. This is the way it should be. Science is not the property of either side. Its accuracy and validity should be scrupulously preserved as the unbiased source of truth. Triers of fact tend to treat it as such and assign great weight to it in reaching decisions as to a defendant’s guilt or innocence. Where the conclusions of a procedure are overstated or erroneously reported, the consequences are often wrongful conviction. And, not all will be able to have a retrial when the errors are ultimately discovered. According to the joint press release, in nine cases in which flawed testimony concerning hair analysis was identified, the defendant had already been executed.

Continue reading below

The review process does not extend to microscopic hair analysis performed in state laboratories. We encourage the states to set up review procedures based on the model established by the FBI, DOJ, IP, and NACDL. Obviously, it is the right thing to do.


  1. National Academy of Sciences, Strengthening Forensic Science in the United States: A Path Forward [hereinafter NAS Report] (2009).
  2. NAS Report, at 160.
  3. NAS Report, at 161.
  4. See Norman L. Reimer, The Hair Microscopy Review Project: An Historic Breakthrough for Law Enforcement and a Daunting Challenge for the Defense Bar, The Champion, July 2013 at 16.
  5. Partnering with The Innocence Project in this effort were David Koropp, partner at Winston & Strawn LLP, and his colleagues, and Michael R. Bromwich, managing principal of the Bromwich Group.
  6. Id.
  7. Press Release, The Innocence Project, FBI Testimony on Microscopic Hair Analysis Contained Errors in at Least 90 Percent of Cases in Ongoing Review (April 20, 2015),
  8. Press Release, The Innocence Project, In Landmark Decision, Massachusetts Court Vacates Conviction Based on Erroneous FBI Microscopic Hair Testimony (Feb. 3, 2016),
About the Author

A certified criminal law specialist, E.G. “Gerry” Morris has been practicing criminal defense law for 37 years. His practice focuses primarily on trials in state and federal courts, but he also handles state and federal appeals as well as post-judgment actions. He is a frequent lecturer at continuing legal education programs.

E.G. Morris
Law Office of E.G. Morris
2202 Lake Austin Blvd.
Austin, TX 78703
Fax 877-497-8347

Featured Products