Saturday, September 12, 2015

Resources on DNA mixtures

Following up on Grits' post about problems with DNA mixture interpretation in criminal cases, I ran across a resource page from the National Institute of Standards and Technology on the topic. Anyone interested in the issue should check it out.

Also, on page 4 of this public defender newsletter out of New York there's a discussion of DNA mixture issues as they're arisen in that state, particularly focused on some of the software used. The newsletter also mentioned a Brooklyn case where a judge refused to allow certain DNA-related techniques to come into court as evidence. In particular: the court found that "evidence based on low copy number (LCN) or high sensitivity analysis of DNA mixtures and results from the New York City Office of the Chief Medical Examiner’s Forensic Statistical Tool (FST) about those mixtures are not generally accepted in the relevant scientific community."

These resources show the DNA mixture issue has been brewing for a while, but it really came to a head when Texas prosecutors had old analyses recalculated and found large changes in the resulting probabilities that evidence matched the suspect. That promoted the issue from a theoretical crisis to an actual, immediate one.

MORE: See the Texas Tribune's initial coverage of potential fallout from the DNA mixture SNAFU.


Anonymous said...

Good to read your post, Scott.

DNA has never been the be-all-and-end-all many would like it to be. The potential for forensics errors and malfeasance, prosecutor bias and witch hunts based political, vested interests will always be with us no matter how good the technology becomes.

One thing is certain: doctors and district attorneys both bury their mistakes.

The Crimes of the Crime Labs:

In Praise of the Statute of Limitations in Sex Offense Cases:
<a href="></a>

Anonymous said...

Broken link above:
In Praise of the Statute of Limitations in Sex Offense Cases:

Anonymous said...

It sucks even more when the DNA comes from a lab analyst self-contaminating the evidence.

Too bad if you're a wrongfully convicted inmate looking for DNA evidence to exonerate you. "Inconclusive results" (because of mishandled evidence and contaminating DNA) means you serve the full sentence.

And ASCLD-LAB thinks this practice of not documenting the semen standards used in the crime lab is perfectly acceptable (so long as the lab does not document contamination events. No documentation means no contamination, right?)