Texas crime labs ill-equipped to handle coming volume of touch-DNA cases

The lede to the Nature News blog article mentioned in the last Grits post described a fascinating occurrence of faulty forensics I hadn't heard about: "Investigators who linked DNA from Occupy Wall Street protesters to a murder scene in New York City recently admitted that they’d made a mistake. No one was locked behind bars, but all too often they are."

Yikes! Yes the DNA will always match if you're repeatedly testing your own! Further evidence, if it were needed, that sloppy lab work can lead to false accusations. (And that lab workers' DNA should be routinely collected.)

Anyway, the link about the Occupy protester leads to a related July 11 story in the New York Times describing the expansion of the use of so-called "touch DNA" by law enforcement, which included these interesting tidbits about New York City's massive, and growing DNA caseload:

The ability to analyze such samples, which are known as “touch DNA,” has allowed investigators to use DNA from scenes where bodily fluids may be absent, Dr. Prinz said. Investigators said that the more heavily the suspect was sweating, the more likely he or she was to leave a useful touch DNA sample.

In 2011, the city medical examiner’s office issued some 11,000 reports involving DNA collected from crime scenes, compared with about 3,000 in 2006, Dr. Prinz said. Reports generally correspond to a single incident, and may involve multiple samples.

Last year, about 32 percent of the incidents in which DNA was sought were property crimes, primarily burglaries and robberies, Dr. Prinz said. Homicides make up only 6 percent of the incidents from which DNA is sought, and sexual assaults are an additional 20 percent. Recovered weapons are swabbed for DNA, too, and account for about 10 percent of the caseload. The remaining cases, Dr. Prinz said, involved DNA taken directly from known suspects for comparison, as well as an assortment of missing person cases, hate crimes, arsons, and other crimes.

In 2011, the medical examiner’s office entered DNA profiles taken from about 2,050 criminal events that year into the F.B.I.’s DNA database. About 24 percent of those resulted in a match against the DNA profiles of known individuals, she said. 

DNA testing in real life is not like on CSI where the computer instantly comes up with a match. In the real world making that determination can take many hours of staff time. This source estimates 54 sequential staff hours per test in a typical rape case; more in a more complicated investigation. DPS labs can process about 518 DNA cases per month, according to a 2010 federal grant request aimed at reducing backlogs. At that time, the agency told the Justice Department, DPS had 75 DNA technicians who could each process about 16.4 samples per month. So this is a labor-intensive process for the lab workers and can't be scaled up quickly.

I don't think Texas' DNA caseloads are quite so laden presently with property-crime cases as in New York, but there's a significant, statewide push from the media and grassroots neighborhoods groups to use crime-labs that way. If they did, they'd both catch more crooks and also generate a few more false positives. But of more immediate importance, it would dramatically boost demand for DNA testing at a time when lab capacity will likely remain flat, at best. Indeed, a new fee-for-service lab in Montgomery County is unexpectedly closing.

Grits expects Texas labs to expand use of touch DNA because the public and local law enforcement will demand it. But I also expect problems to arise including utterly insufficient lab capacity, a lack of qualified, trained personnel (particularly at labs outside the main urban areas), and delays for agencies that don't use fee-for-service labs or perform the work in-house. DPS, to their credit, just finished  a major expansion of their statewide crime lab system. But that hasn't and likely won't eliminate DNA backlogs, which the agency told DOJ have reached as long as 10 months.

Texas has made enormous investments at the state and local levels to expand and professionalize its crime labs over the last seven years. But crime lab volumes are at the beginning of a scary-steep growth curve which, even after those investments, the state appears ill-equipped to handle. In the end, the expansion of DNA use to solve nonviolent crimes will likely be limited by law enforcement's willingness to pay for that service on a per-test basis, which is increasingly the only alternative for waiting months for DPS. From a politicians' perspective, that's when "tuff on crime" runs smack dab into "no new taxes."