Once samples from all sources are in hand, analysts isolate a bit of DNA from each sample, make lots of copies of it, and then process the copies through a machine that analyzes genetic markers — DNA fingerprints — that have been passed down through a subject’s family. Typically, Bieber said, DNA tests examine around 15 of these markers.
It typically takes several hours to complete each step of the analysis process, Bieber said, though he noted that in high-profile cases like this one, law enforcement agencies might already have genetic profiles of the relatives available — which means they’d only have to complete one additional test.
I checked and it seems that there are paternity testing outfits that offer one day turnaround. So I guess it’s not implausible that they could have pulled this off. I assume they still use variable number tandem repeats for DNA profiling?
Update: Yeah, short tandem repeats.
I already blogged this general issue, but the ‘grim sleeper’ murderer was caught because of a match of old samples with those of us his son. If I had to bet money I think this sort of result (California and Colorado are the two American states which have a system in place to allow for this) is going to allow for a push toward more widespread usage of the technique. It may be that we need to stop talking about privacy as if we can put off the inevitable future, and start talking about accuracy and precision with the data that is going to be easily available to authorities. By the way, I found this objection somewhat strange:
“I can imagine lots of African-American families would think it is not fair to put a disproportionate number of black families under permanent genetic surveillance,” said Jeffrey Rosen, a law professor at George Washington University who has written about this issue.
A disproportionate number of black families have relatives incarcerated. The American public does not seem particular worried about that. As I noted before, criminal behavior is not randomly distributed across families. Rather, there are distinct clusters, so familial genetic data is going to be more efficacious than you would expect if the commission of crime consisted of a sequence of independent events.
I have to add that worries about this technology strike me as a bit rich, in light of the fact that methods which are proven to be highly subjective and often inaccurate, such as fingerprinting and eyewitness identification, are accepted in the criminal justice system. I worry about what the state could do with DNA data if the state became malevolent, but despite its flaws it seems to me far preferable as a means of assessing evidence than some of the “tried & true” techniques. So let’s keep some perspective.