Thursday, August 12, 2010

Time to Re-Write All Those CSI Shows

Oh, well.

We took a mixed sample of DNA evidence from an actual crime scene- a gang rape committed in Georgia, US- which helped to convict a man called Kerry Robinson, who is currently in prison. We presented it, and Robinson's DNA profile, to 17 experienced analysts working in the same accredited government lab in the US, without any contextual information that might bias their judgment.

In the original case, two analysts from the Georgia Bureau of Investigation concluded that Robinson "could not be excluded" from the crime scene sample, based on his DNA profile. (A second man convicted of the same crime also testified that Robinson was an assailant, in return for a lesser jail term.) Each of our 17 analysts independently examined the profiles from the DNA mixture, the victim's profile and those of two other suspects and was asked to judge whether the suspects' profiles could be "excluded", "cannot be excluded" or whether the results were "inconclusive".

If DNA analysis were totally objective, then all 17 analysts should reach the same conclusion. However, we found that just one agreed with the original judgment that Robinson "cannot be excluded". Four analysts said the evidence was inconclusive and 12 said he could be excluded.
--New Scientist, quoted at Bayou

Does this mean that it will take longer than 48 minutes to solve crimes??

1 comment:

Anonymous said...

Of course there are going to be errors in science.

What is SUBJECTIVE are the standards used to draw conclusions based on the samples. In that same article, the author stated that forensic lab directors would welcome "interpretation procedures based on national standards". Therefore, the guidelines on how to interpret the samples must be CONSISTENT and UNIVERSAL. Therefore, it is not surprising that there were different conclusions.

Forensic DNA analysis experts have recently published new recommendations which ought to be adopted. Regardless of its "imperfections", DNA testing remains a powerful tool for law enforcement agencies.