Holding your hands up and saying 鈥渨e got things wrong鈥� is a difficult thing to do. But that鈥檚 exactly what the FBI and US Department of Justice have had to do this week, as the initial results were released of an ongoing review of thousands of criminal cases in which FBI scientists鈥� testimony may have led to wrongful convictions 鈥� including for some people now on death row.
In the 1980s and 1990s, forensic scientists routinely compared hairs under the microscope, looking for physical similarities that might indicate a hair recovered from a crime scene came from a suspect. This still happens today, but it is usually backed up by mitochondrial DNA testing.
Two years ago, the FBI launched an inquiry into 2600 convictions, including 45 death-row cases, from the 1980s and 1990s, looking for instances where FBI analysts may have exceeded the limits of science when presenting their conclusions in court 鈥� saying a hair matched to the exclusion of all others, for example, rather than simply saying it looked similar.
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This week it was reported that of the 10 per cent of cases reviewed so far, the 鈥渧ast majority鈥� contained errors. As a result, 136 defendants, including two on death row, will receive letters informing them of their right to DNA testing as a means of proving their innocence. This is in addition to 23 letters that went out last year, including to 14 people on death row.
Landslide triggered
This could just be the start. Some think that the FBI鈥檚 admission could trigger a landslide of similar cases involving state labs that also performed hair analysis 鈥� many of which were trained by the FBI. It could even ripple out to other areas of forensic science that don鈥檛 fall under the current review.
Already, state labs in Texas, North Carolina and New York have launched similar reviews of convictions involving hair analysis. 鈥淚 think it鈥檚 just the tip of the iceberg,鈥� says Peter Neufeld, co-director of the in New York City, which fights to exonerate wrongfully convicted people through DNA testing. 鈥淭here鈥檚 no question that it鈥檚 going to affect state labs as well.鈥�
Of the 317 DNA exonerations in the US so far, 75 of the original convictions included testimony from hair analysts 鈥� and of these, 70 involved experts from state labs, rather than the FBI lab. 鈥淢ost had some kind of scientific errors in their testimony,鈥� Neufeld says.
鈥淣obody who attended any of the FBI classes was told to over testify, that鈥檚 not part of the training,鈥� says Max Houck, a former FBI hair analyst who taught some of these classes and now heads the in Washington DC. 鈥淗owever, our fear was always that we teach these people for two weeks, and they would go back to their laboratories with a certificate of completion and be told: 鈥楪reat you鈥檙e qualified to do this 鈥� here鈥檚 your caseload.'鈥�
Visual comparisons
Yet hair analysis is just one of many forensic disciplines that hinge on using a microscope to visually compare two samples and declare a match. Ballistics, fibre analysis, tyre and shoeprint comparison and tool and bite-mark analysis all take a similar approach. All came under heavy criticism in a landmark report on the state of forensic science published in 2009.
鈥淭his review is likely to have an effect on any discipline where they didn鈥檛 have a statistical reference to estimate the chances of another person being a match,鈥� Neufeld says. He believes it could even filter across to disciplines with a more robust statistical basis such as fingerprinting, but which have been exposed as flawed in recent years.
Of course, in many of the cases under review, there may have been additional evidence that might have seen the person convicted. 鈥淭he review does not evaluate if a potentially erroneous statement was material or relevant to the conviction,鈥� an FBI spokeswoman told New 杏吧原创.
Neufeld admits that we don鈥檛 yet know how many convictions were gained on the back of erroneous statements. 鈥淚n almost no case is a person convicted on just a single piece of evidence,鈥� he says. However, he adds that before DNA testing, a matching hair would often be a crucial point that prosecutors would emphasise in their closing remarks. 鈥淐ombined with an unreliable eyewitness statement, it could create a perfect storm,鈥� he says.
