Nova Forensics on Trial (1974– ) Online

It was discovered recently that not all snowflakes are unique. (And why should they be?) Some are the same as others. As this program illustrates, for all practical purposes fingerprints have been treated as unique whereas in forensics false matches crop up. The initial case is that of some poor nerd named Mayfield who lived in Portland, Oregan, and was Islamic, although you'd never know it from looking at him. He's the prototype of the guy who sits across the desk from you at H&R Block.

Al Qaeda has blown up several bombs in a railway station in Madrid, Spain. A fingerprint was left on a plastic bag, the FBI matched it to Mayfield, and he was convicted because there were a sufficient number of matching "points". It was only after Mayfield had spent some time as a guest of the state that the Spanish police were able to match the print to the correct individual, a known terrorist. Mayfield got out.

Mistakes are also made in matching dental patterns from bites and other forensic technique. Real criminals are going free while innocent people are in the slams.

But the program takes us through some striking strides being made in forensic techniques. The explanations are easy to follow. The techniques are far more accurate but of course more expensive and their use doesn't appear to be widespread yet.

One of these techniques, now used in Sweden, combines CT and MRI scans of a dead body to perform a virtual autopsy that can expose evidence that would escape an ordinary autopsy, such as gasses that might build up after a strangulation. You don't even have to remove the cadaver from the body bag. The program doesn't mention it but some data are also lost in this procedure. The pathologist doesn't have the pleasure of sniffing the stomach contents for evidence of poisoning, for instance.

I suppose most of us have heard of "blood spatter" evidence, but I, for one, didn't know that a careful examination could indicate the kind of weapon, the number of blows and their violence, and the actually source of the blood. (Eg., if it's mixed with water, it's likely from the mouth.) The O. J. Simpson double murder is presented as a case study in how to screw up a crime scene and compromise incontrovertible evidence.

Of course there will always be a subjective element in interpreting the data. The human mind has its hard-wired limitations.