Midwest Innocence Project’s review of microscopic hair comparison cases


FBI Review – Need for review at the state level

In 2012, the Federal Bureau of Investigation, the National Association of Criminal Defense Attorneys, the Innocence Project, and the Department of Justice undertook a large scale review of microscopic hair comparison cases conducted by analyst agents at the FBI’s Quantico Laboratory. The review revealed that, in at least 90% of cases reviewed, analysts testified in ways that exceeded the limits of science. Hundreds of regional analysts were trained by the FBI over at least two decades, necessitating a review of cases at the state level.

MIP is conducting a similar review of microscopic hair comparison cases in its five-state area of practice, which includes Iowa, Kansas, Missouri, Arkansas, and Nebraska. MIP’s approach to this review utilizes the error types developed for the FBI and gathers further data on the language used by prosecution and defense counsel in opening and closing statements and the timeline of forensic science reports to identify situations of potential cognitive bias.

The 3 Error Types – Why they matter

The FBI review categorized the problematic testimony into three error types:

  • an analyst identified or implied an identification of a hair to an individual;
  • an analyst stated or implied a statistical weight to the association of the hair to an individual; or
  • an analyst used their own experience in the lab to imply a de facto statistical significance to the association.

The lack of statistical underpinnings for claims made by forensic analysts in testimony and in laboratory reports preceded the FBI’s review. In fact, the gaps in that knowledge were addressed at length in a 2009 National Academy of Sciences Report, which states “No scientifically accepted statistics exist about the frequency with which particular characteristics of hair are distributed within the population”, meaning that two hairs can look exactly the same under the microscope, and we have no way of knowing how frequently that happens.

Click here to read more about microscopic hair comparisons.


MIP recognizes and embraces the need to work in partnership with others in order to conduct a timely and robust review of cases. Based on the model of the national review, MIP seeks to work with laboratories, experts, and criminal justice stakeholders in our region.

We are currently working with the Iowa State Public Defender’s Wrongful Conviction Division (WCD), which has been empowered by Governor Terry Branstad to address cases where this problematic testimony may be present. To this end, MIP, WCD, and the Iowa Division of Criminal Investigation’s Criminalistics Lab have partnered to identify cases involving hair analysis. MIP and WCD are collecting transcripts and putting together a team of experts to review them. Together, we want to assure that no innocent Iowans remain in prison, and that forensic science is practiced with the highest levels of accuracy in the state of Iowa.

What the review looks like in Iowa

Iowa Department of Corrections data listing all currently incarcerated inmates was given to the DCI Crime Lab to determine if hair evidence was collected in any of those cases. WCD and MIP used lab reports from DCI to determine if a microscopic comparison of hairs was conducted. If so, those defendants were each sent written notification of the review and given an opportunity to make an innocence claim. Cases will be reviewed for error, however, litigation and DNA testing will be prioritized based on cases with factual innocence claims.

Because the errors in hair comparison reports and testimony are rooted in a lack of statistical data, we are in the process of collaborating with experts in the field of statistics in order to determine the extent to which analysts testified to the likelihood of an association in an erroneous way. We are also seeking experts in cognitive bias, both to review cases for instances where hair analysts were subjected to contaminating information, and also to assure that our review design does not bias our statistician collaborators.


In February of 2016, the FBI Director sent a letter to Governors to ask for their continued cooperation in the national review and to encourage them to assure that analysts in their state laboratories were testifying in an appropriate way. Further, the American Society of Crime Lab Director’s Laboratory Accreditation Board, the organization that awards accreditation to crime labs in the United States, recommended that each lab consider reviewing past cases because they have an ethical obligation to “take appropriate action if there is potential for, or there has been, a miscarriage of justice due to circumstances that have come to light.”

Submit a case or contact the project

If your case or the case of your family member included a microscopic hair comparison, your organization conducted microscopic hair comparisons or represented or prosecuted defendants in whose cases these comparisons took place, you are located within our five-state area of practice, and you would like to work together on this review, or request a review of your case, please contact MIP to discuss the potential for collaboration. E-mail at office@themip.org or call at 816.221.2166.