Cold cases

 Michael - Alternate Thursdays

Why are cold cases so fascinating? Look at the popularity of all the fact-based TV series complete with interviews with the actual investigators and witnesses. One obvious reason is that because the cases take so long to solve, they tend to be twisty and surprising. Otherwise they wouldn’t be cold cases in the first place. Maybe the fact that the detectives are initially baffled and only new evidence or new technology allows them to make a breakthrough adds to the interest. Whatever the reasons, cold cases grab attention. And there are plenty of them in plenty of varieties. For a selection take a look at Wikipedia.

Mystery Fanfare's take on cold cases...

It’s conventional wisdom that a case that’s going to be solved at all is usually solved in two days. Actually, investigators say that more accurately a person of interest is identified in that time period, and a couple of weeks is all that’s required to gather enough evidence so that the person can be arrested. (Generally, Forensics needs longer than a few days to process all the evidence, and DNA may take longer still.) A Washington Post examination of 8,000 homicide arrests across 25 major U.S. cities since 2007 found that in half of the cases an arrest was made in ten days or less.

Still, in a murder case, the police would expect the case to stay “warm” for about a year before it gets relegated to the cold-case division. That would be another group of detectives (maybe just one) who will go over the casefile again in detail and try to see the evidence from a different perspective and throw a wider net to pick up suspects. Unsolved murder cases never close, but their probability of being solved rapidly decreases. Given the amount of effort that has already been put into the case while it's "warm", it’s rather surprising that around 30% of cold cases are actually solved in a year. However, the number of cold cases keeps growing.

 

The driving force behind solving cold cases may well be a new technology rather than a new pair of eyes. The common use of DNA testing was a huge boon and became standard at crime scenes around 2000, making the early 2000s the heyday of cold-case units. There was a huge amount of stored evidence, some of which could be DNA tested leading to connections with existing suspects or introducing new ones. However, of course, the DNA requires something to match to. If the murderer had left a DNA signature (more likely in those days before killers regarded CSI as required viewing for Murder101), then it didn’t help unless Forensics had a matching sample from an identified person. In fact, DNA was often more helpful in eliminating suspects than it was in identifying new ones. DNA analysis was (and still is) a huge boon for exonerating innocent people.

Joseph DeAngelo, the Golden State Killer
This charming old gentlemen murdered and raped at least 65 people

More recently the internet and people’s love of using it has offered a rather different sort of database – a sort of “volunteer” DNA databank. One of these is GEDmatch. Started by one man to help people find lost family members and ancestors, it allows you to upload your DNA markers, and then you can search it for various types of matches. It can identify quite distant or close relatives. So one can find a lost third cousin or perhaps fill gaps in a family tree. In the wide open world of social media, there’s no downside. But there is one of course. Other people can also search and discover you as a relation. Even the police can search by uploading the DNA of an unknown suspect. Zoe Sharp explained how it was used to catch the Golden State Killer in 2018 in one of her blogs.

At the time the owner of GEDmatch was furious that his site had been used in that way, fearing he’d lose many of his clients because of the feeling that they were being analyzed in some way by the police. Big Brother is watching your DNA. However, he was wrong. The reaction of his clients was overwhelmingly positive. Now you can opt out of being visible to law enforcement agencies, but most people don’t seem to mind. Perhaps discovering that your cousin is a murderer is not only worth a viral Facebook post, but may be a useful safety feature! Then again, perhaps people just like the idea of helping the police.

The AI detective
Yes, it does exist. No, it doesn't look like this.

So where will the next cold case breakthrough technology come from? The AI detective? I wrote a science fiction short story along those lines fifty years ago, maybe I should dust it off…