“I see,” is all she says.
“See? What the hell do you see?”
“I see you know,” she answers me. “Question is, how?”
I tell her about the Tlip file. I inform her that it appears Benton had the documents checked for fingerprints and I am wondering who did that and where and what the results might have been. She has no idea but says we should run any latent prints through the Automated Fingerprint Identification System, known as AFIS. “There are postage stamps on the envelopes,” I inform her. “He didn’t remove them and he would have had to if he wanted them checked for DNA.”
It has only been in recent years that DNA analysis has become sophisticated enough, because of PCR, to make it worthwhile to analyze saliva, and just maybe whoever affixed postage stamps to the envelopes did so by licking them. I am not sure that even Carrie would have known back then that licking a stamp might give up her identity to us. I would have known. Had Benton showed these letters to me, I would have recommended he have the stamps examined. Maybe we would have gotten results. Maybe he wouldn’t be dead.
“Back then a lot of people, even those in law enforcement, just didn’t think about things like that.” Berger is still talking about the postage stamps. “Seems like all cops do these days is follow people for their coffee cups or sweaty towels, Kleenex, cigarette butts. Amazing.”
1 have an incredible thought. What she is saying has brought to mind a case in England where a man was falsely accused of a burglary because of a cold hit on the Birmingham-based National DNA Database. The man’s solicitor demanded a retest of the DNA recovered from the crime, this time using ten loci, or locations, instead of the standard six that had been used. Loci, or alleles, are simply specific locations on your genetic map. Some alleles are more common than others, so the less common they are and the more locations used, the better
your chances for a matchwhich isn’t literally a match, but
rather a statistical probability that makes it almost impossible to believe the suspect didn’t commit the crime. In the British case, the alleged burglar was excluded upon retesting with ad- ditional loci. There was a one-in-thirty-seven-million chance of a mismatch, and sure enough, it happened.
“When you tested the DNA from Susan’s case, did you use STR?” I ask Berger.
STR is the newest technology in DNA profiling. All it means is we amplify the DNA with PCR and look at very discriminating repeated base pairs called Short Tandem Repeats. Typically, the requirement for DNA databases these days is that at least thirteen probes or loci be used, thus making it highly improbable that there will be any mismatches.
“I know our labs are very advanced,” Berger is saying. “They’ve been doing PCR for years.”
“It’s all PCR unless the lab is still doing the old RFLP, which is very reliable but just takes forever,” I reply. “In 1997, it was a matter of how many probes you usedor loci. Often in first screening of a sample, the lab may not do ten, thirteen or fifteen loci. That gets to be expensive. If only four loci were done in Susan’s case, for example, you could come up with an unusual exception. I’m assuming the ME’s office still has the extraction left in their freezer.”
“What sort of bizarre exception?”
“If we’re dealing with siblings. Brothers. And one left the seminal fluid and the other left the hair and saliva.”
“But you tested Thomas’s DNA, right? And it was similar to Jean-Baptiste’s but not the same?” I can’t believe it. Berger is getting agitated.
“We also did that just days ago with thirteen loci, not four or six,” I reply. “I’m assuming the profiles had a lot of the same alleles, but also some different ones. The more probes you do, the more you come up with differences. Especially in closed populations. And when you think of the Chandonne family, theirs is probably a very closed population, people who have lived on Ile Saint-Louis for hundreds of years, probably married their own kind. In some cases, inbreedingmarrying cousins, which might also account for Jean-Baptiste Chandonne’s congenital deformity. The more people inbreed, the more they up their chances for genetic glitches.”