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Tuesday, September 30, 2008

Science and society: The assured results of modern forensic science ... ?

We've all seen the detective films where the forensic scientist is always a source of useful information about the crime, right? I'm a great fan of such films myself, Brit lit P.D. James being one of my favourite mystery stars. For psychological insight, she is rarely matched.

However, in real life, if you are accused of a crime to which forensic evidence is relevant, things may be quite different. If you know you are innocent, you might be well advised to pray hard that the forensic team is any help.

In "C.S.Oy" in Slate (August 12, 2008) Radley Balko and Roger Koppl reveal,


A study of the first 86 DNA exonerations garnered by the Innocence Project estimated that faulty forensic science played a role in more than 50 percent of the wrongful convictions.
Here are two of their recommendations for reform:

Expert independence. Crime labs, DNA labs, and medical examiners shouldn't serve under the same bureaucracy as district attorneys and police agencies. If these experts must work for the government, they should report to an independent state agency, if not the courts themselves. There should be a wall of separation between analysis and interpretation. Thus, an independent medical examiner would, for instance, perform and videotape the actual procedure in an autopsy. The prosecution and defense would then each bring in their own experts to interpret the results in court. When the same expert performs both the analysis and interpretation, defense experts are often at a disadvantage, having to rely on the notes and photos of the same expert whose testimony they're disputing.
and

Mask the evidence. A 2006 U.K. study by researchers at the University of Southampton found that the error rate of fingerprint analysts doubled when they were first told the circumstances of the case they were working on. Crime lab technicians and medical examiners should never be permitted to consult with police or prosecutors before performing their analysis. A dramatic child murder case, for example, may induce a greater subconscious bias to find a match than a burglary case. To the extent that it's possible, evidence should be stripped of all context before being sent to the lab...
Incompetent or corrupt investigators can pervert the course of justice by definition, but Balko and Koppl reveal a deeper, more serious problem: Well-meaning and competent investigators who are influenced by their bosses' views or cultural assumptions may be far more damaging in the long run because ... everyone believes them!

After all, science is modern society's source of truth! And they are hey are sincere and competent, and not corrupt ...

But they may not recognize their own cognitive biases. Nor might others.

Balko and Koppl add

Every other scientific field properly requires peer review, statistical analysis, and redundancy to ensure quality and accuracy. It's past time we applied the same quality-control measures to criminal forensics, particularly given the fundamental nature of what's at stake.
I myself would place more confidence in statistical analysis and redundancy than in peer review (who are the peers?) but it is all worth a try, in principle.

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