Saturday, December 11, 2010

Unscientific fingerprint evidence

The NY Times reports:
Researchers have found a way to mathematically calculate the rarity of a fingerprint.

Although fingerprints are unique to every individual, crime scene prints are usually incomplete patterns taken off doorknobs or glass. ...

Today, forensic scientists make this call without the aid of technology.

“They might find hundreds of prints at a crime scene, and right now the analysis is done intuitively by human examiners,” Dr. Srihari said. “But we can calculate that.”
This is news? FBI criminologists have been giving bogus fingerprint testimony for decades. The Federal Rules of Evidence say:
Rule 702. Testimony by Experts

If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.
If the "forensic scientists" are making their calls without technology, then they are not scientists, and they are not following FRE 702. Their testimony should be inadmissible.

Making mathematical calculations to assess the reliability of fingerprint evidence is not difficult. Other countries do it. It is a scandal that American prosecutors do not. Jurors should be trained to reject any evidence from witnesses who refuse to give any measure of its reliability.

Here is a typical court justification
of sloppy fingerprint evidence:
In Baines , the defendant-appellant challenged a fingerprint analyst's expert methodology. The district court held the expert opinion testimony of fingerprint analysis relevant and reliable, noting that the subjectivity of the analysis goes to the "weight of the evidence, not its admissibility," and that the weight of the evidencecould be attacked during trial. After conducting a Daubert review of the record, the Tenth Circuit affirmed the admissibility of the expert witness based on his technical knowledge. The court emphasized that an independent scientific method to verify fingerprint analysis would be "all to the good. But to postpone present in-court utilization of this 'bedrock forensic identifier' pending such research would be to make the best the enemy of the good."
This is ridiculous. The research is available. The prosecution just prefers to avoid it, if they can get away with it.

No comments: