Crime lab bias

medium_4426655557When I worked in the lab, we would receive offense reports from law enforcement containing information on the crime. While it would be ideal not to have to rely on reports/allegations for testing in order to remove all potential for bias, it’s just not practical. The lab needs some idea of what might have occurred to know which biological fluids might be important. In some cases it is obvious; in others, you have no idea.

Let’s say a woman was attacked by a man and her clothing was submitted. You know nothing about the case, so you do the normal analysis for blood and/or semen and find nothing. But the offense report says the woman was bit on her shoulder before managed to get away from her attacker. Now the lab would know to look for evidence of saliva on the woman’s shirt. If you find it and the stain yields a male DNA profile. Voila! If the lab didn’t know that the complainant had been bitten, they might have missed an important stain.

Now, does that mean that the saliva stain on the woman’s shirt is the only stain that should be analyzed? Not at all. It should definitely be analyzed, but other positive stains should be analyzed as well. This is the most likely place you’ll run into bias in a crime lab. Because laboratories deal almost exclusively with detectives and prosecutors, and because many crime laboratories are under-budgeted and understaffed, some labs only analyze “the most probative samples” (i.e. samples likely to have the highest evidentiary value in court) to cut down on the time and expense of case analysis.

The problem with this picking-and-choosing approach is that only a portion of the results are reported. If several swabs from a sexual assault kit are positive and only one item is tested, what about the others? What if they would have given a different result? Another male profile? Or what about our case example from above. What if the man’s semen was found on samples taken at the hospital? Could it be that the woman was trying to cover for a clandestine affair that she didn’t want her husband to know about? Instead of fessing up, what if she fabricated a “crime”? 

photo credit: West Midlands Police via photopin cc
photo credit: West Midlands Police via photopin cc

There have been rogue forensic scientist who have made up results or testified beyond the limits of science in order to aid the prosecution. A few notable examples are Joyce Gilchrist from Oklahoma and Fred Zain from Texas and West Virginia, among others.

Crime lab bias is the main reason why some believe that crime labs should not be under the administration of police departments or law enforcement agencies. If the lab’s “clients” are law enforcement, then it is natural for the lab to want to “help” officers and attorneys. And sometimes that help can get our of control, as in the case of Joyce Gilchrist and Fred Zain, among others. If the lab answers to the Chief of Police, can you see the potential for bias in high profile cases? 

In my experience, crime lab staff, law enforcement, and prosecutors are more interested in what the science says about the crime than in having the science match what they think occurred. No one wants to put innocent people behind bars. Forensic science is a tool to aid law enforcement in tracking down the truth.

Next time, we’ll talk about DNA exoneration and the Innocence Project. Stay tuned. 🙂

But for now – what questions do you have?


3 thoughts on “Crime lab bias

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