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Microscopic Hair Comparison Review Project

To date, more than 300 people have been proven innocent through DNA testing, which in most cases did not exist or was not available at the time of their convictions.  In almost ¼ of the DNA exonerations (just over 70 defendants), the prosecution used hair microscopy evidence to link the defendant to the crime.  Advances in science, specifically the advent of mitochondrial DNA testing (DNA testing on hair without a root), revealed that examiners reported false hair matches in those specific cases.   

championFor decades, the FBI Crime Lab has conducted hair microscopy, where an examiner uses a high powered microscope to view hair from a crime scene and compare it to a known hair sample.  Looking for similarities in each hair, if enough characteristics are the same, the examiner deems the hair a “match”.  Further, in making comparisons, examiners use a “sample” (approximately 10) hairs from the known subject to compare with an unknown hair to see if characteristics from the unknown hair are present in the array of known hairs.  Thus, it is not a one to one comparison, but rather a one (unknown hair) to many (known hair sample) comparison to search for similar characteristics.  

Scientists have criticized this forensic discipline and noted its limited reliability based, in part, on the unknown pool of subjects with the same hair characteristics.  In the late 1990s, and the use of mitochondrial DNA testing, the FBI crime lab limited its use of hair microscopy and used it only in conjunction with DNA testing to confirm results.    

Following a trio of DNA exonerations in Washington DC (from 2009-2012), all three defendants were convicted on FBI microscopic hair comparison evidence which turned out to be wrong, the FBI commenced an internal review of microscopic hair analysis cases to determine the extent to which flawed evidence may have tainted convictions. The FBI estimates that approximately 21,000 cases involved microscopic hair analysis will be reexamined.  In July of 2012, the Department of Justice publicly announced this historical review and noted that the review will include collaboration with the Innocence Project and NACDL.  The involvement of prominent defense organizations is vital for two reasons: it underscores the non-adversarial nature of the review process and it facilitates the identification of those who were affected by the flawed evidence and the procurement of transcripts essential to the review process. /uploadedImages/Content/Criminal_Defense_Issues/Post-Conviction_Projects/sm_©RoyaltyFree_ingimage_DOJ_03B87119.jpg 

The review begins internally at the FBI crime lab identifying cases with a “positive” association of hair analysis (allegedly linking the defendant to the crime scene or to the victim).  Next, the FBI reviews the lab reports and the trial testimony from the FBI examiner (if the defendant went to trial rather than pled guilty).  The reviewers identify errors in the reports and/or testimony:  “errors” involve statements exceed the limits of science and/ or overstate the conclusions that may appropriately be drawn from a “positive association” between evidentiary hair and a known hair sample.  Once errors are identified by the reviewers at the FBI lab, the results are sent to the IP and NACDL for independent review.  Ultimately, a report is generated identifying the errors in the lab report and/or trial testimony, and the defendant is notified via current counsel or last known counsel.    

Due to the nature of post-conviction review, the majority of the affected defendants no longer have an attorney and most are not entitled to an attorney at the government’s expense.   Thus, NACDL has committed to finding counsel, on a pro bono basis, to review cases identifying any potential post-conviction claims a defendant may bring (under the appropriate state or federal post-conviction relief law) and represent those defendants in court.    

Our Partners

Federal Bureau of Investigations 

The Innocence Project 

Recent Exonerations


The Washington Post  

An in-depth series by Spencer Hsu on the Review covering the flawed evidence, exonerations, and the DOJ/FBI investigations.

Al Jazeera America  

The New York Times  

The Guardian 


The Atlantic 

Ars Technica  

PBS News Hour 

CBS News 

Litigation Support

Are you involved in a microscopic hair comparison case? Register for the Hair Comparison Litigation Group. 

Post-Conviction Innocence Claims Toolbox 

Forensic Resources 

Pro Bono Partnership Project

NACDL is actively seeking lawyers willing to represent Microscopic Hair Comparison Review project defendants pro bono. NACDL has formed a number of significant partnerships with law school clinical program, major law firms, and individual criminal defense attorneys. Interested attorneys can volunteer pro bono service to affected defendants in a number of ways, including reviewing documents, investigating wrongful conviction claims, and litigating cases.

For more information, or to discuss a pro bono partnership, please contact  Vanessa Antoun  

State Microscopic Hair Comparison Reviews

The FBI/DOJ Microscopic Hair Comparison Review examines only the work done by FBI hair analysts. However, the FBI analysts in question trained state and local forensic investigators in the same flawed techniques that are the subject of the FBI/DOJ review. Several states have begun to examine the work of state hair analysts.




North Carolina

Kansas City 


State Review News 

  • The New York Times, Lives in the Balance, Texas Leads Scrutiny of Bite-Mark Forensics, December 12, 2015
  •  The Des Moines Register, Branstad: State Will Investigate Wrongful Convictions, October 26, 2015
  • Iowa Public Radio, Exonerating Wrongful Convictions: Iowa's Innocence Project Forges New Partnerships, October 27, 2015
  • The Washington Post, Review of FBI Forensics Does Not Extent to Federally Trained State, Local Examiners, December 22, 2012
  • Kansas City University Radio, Kansas City Artist Uses Creative Skills to Review Criminal Cases, October 1, 2015
  • WCVB 5 News, State Launching Review of Convictions to Find Faulty Hair Forensics, May 14, 2015

  • For more information and resources, or to start a state microscopic hair comparison review, please contact Senior Resource Counsel Vanessa Antoun 


    Vanessa Antoun 
    Senior Resource Counsel





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