Jeff Gamso tells us: 6.17 quadrillion to 1. He also tells us why they don’t mean what they say. Despite the numbers crunching, the certainty of experts and the desire for judges and juries to have the hard decisions lifted off their shoulders by the experts who assure them that there is no way, none, that the defendant isn’t the bad guy, Jeff also explains why criminal defense lawyers need to go old school and listen to our clients.
What got me started on this, though, wasn’t Balko’s piece at Slate. It was Walter Reaves of Texas and his discussion of what happened in Ohio last week.
It’s about Stephen Myers. That’s the factually innocent Stephen Myers.
In Myers’ case, prosecutors decided to retest the DNA, even though it had already proven conclusively that Myers was the guy in tests 10 years earlier. The retest turned out differently. Myers suddenly wasn’t the guy who committed the home invasion. Up to then, there were only two people who were sure about the outcome, Myers and the guilty person.
It’s a fluke, an oddity, that the prosecutors decided to retest. Reaves sees in this story not just a prosecutor who did the right thing, but a lesson for defense lawyers. When your client insists on his innocence, and after you’ve had a heart-to-heart about what testing might prove still wants it done, you should have it done.
Don’t trust the prosecutor to do your homework for you – or, sadly, to give you the good news if she does. Maybe. But maybe not. Regardless, defense counsel have a duty to investigate, not merely to trust that the prosecutor got it right.
After a while, we begin to feel that we’re just a cog in the wheel of justice, part of the system that populates courthouses on a daily basis. We feel more aligned with the system than our clients. We see the trends, the norms, the way things usually go, and it can save us a lot of time and effort to just go with it. After all, what are the chances that anything could go wrong?
Whether the chances of a DNA mismatch are 6.17 quadrillion to 1 or less, the protestations of our clients count. Sure, there’s a good chance that their demands will sink them, although it’s never clear that they can be sunk more than they already are. It’s just that we’re never an arm of the prosecutor or the court, even if that means we have to turn down the opportunity to be one of the gang at court.
Sure, the odds are against us. Very much so. Chances are that the retest will be a waste of money and just more evidence to nail the lid even tighter on our client. But when the client insists he’s not the guy. When the client squeezes your arm and says, “please, you gotta do this,” there’s no choice in the matter. In all likelihood, the test will reaffirm the defendant’s guilt. But what if your client is Stephen Myers? You can’t take that chance, no matter how easy it is to do nothing.
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I question the validity of that 6 quadrillion to one estimate. There have been too many other instances of mistaken matches [link deleted].
DNA itself may not match except at those ratios, but they only check 13 loci and the odds of those matching are apparently higher to judge by the actual number of redundant profiles found. In Maryland, “In a database of fewer than 30,000 profiles, 32 pairs matched at nine or more loci. Three of those pairs were identical at 13 out of 13 loci.” A 10,000 – 1 ratio is daunting, but it ain’t 6 quadrillion.
I believe that was one of Jeff Gamso’s points, to reject the oddsmakers who proclaim near-certainty when there are so many factors that undermine the accuracy of their numbers game.
I did some back-of-the-envelope calculations about DNA matching a few years ago, and I don’t believe finding 32 pairs that match at 9 or more loci out of a collection of 30000 is inconsistent with the usual odds given for DNA matching. The 13-loci matches are a cause for concern, indicating at least the presence of the same people in the database more than once. It could also be identical twins, although finding 3 pairs in a random sample fo the Maryland population that small seems unlikely.
I posted this to Gamso’s post to, but having not heard a response, and believing this to be one of those truly vexing situations where there is no absolutely right answer, I’d be interested in people’s thoughts on this hypo:
Client against whom there is a fair amount of implicating circumstantial evidence, likely enough to convict in the absence of some explanation that currently does not exist, insists on his innocence. The overwhelming likelihood is that if the client did not in fact commit the crime, one of 3 other people, all of whom have been swabbed, did.
There is an item that is likely to contain the perpetrator’s DNA. Client insists that his DNA will not be on it, after a heart to heart come-to-Jesus, you’re completely fucked if your DNA comes back on this. If the DNA of one of the other 3 people is on the item, it would almost certainly result in a dismissal. Client’s speedy trial right is too close to accomplish the testing without a time waiver and client refuses to waive time.
Do you waive over his objection based on his unwavering claim of innocence and the significant chance that if his DNA is not on the item that case is much better if not gone? Or do you take his refusal to waive time as a passive acknowledgement of the fact that his DNA will probably be on the item and proceed to trial without results?
Obviously, the question is not entirely hypothetical. I have this situation currently and great minds I have consulted disagree. Interested in what you or other CDLs here think?
It’s the client’s call. After the consequences are fully explained and put in writing, as it’s his life and his choice. Have him sign a letter that sets forth the consequences, directing you to do one or the other. This isn’t to exculpate yourself from IAC later, but to make it as clear as possible to the client how serious the consequences will be. And he knows best, especially in these circumstances.
To me, the disturbing thing about this case is that it’s not at all clear that we should be too surprised by a false DNA match when, as here, the probability of a match by chance is 1 in 1.6 million.
We’re told that this is a cold DNA hit, but we’re not told how many DNA profiles they went through to find a match (presumably, as many as possible), and I wasn’t able to turn up anything via Google. The probability of not getting a match for a single profile is 1,599,999/1,600,000. Assuming that the probabilities of false matches for each profile are independent of one another, and assuming further that the actual perpetrator’s profile isn’t in the database used in the search, the probability of doing a cold hit search and not getting a match would be (1,599,999/1,600,000)^n, where n is the number of profiles in the database(s) searched. Or, to restate, the probability of getting a match would be 1 – (1,599,999/1,600,000)^n.
If, for example, n = 250,000, then the probability of a (false) match would be 1 – (1,599,999/1,600,000)^250,000, which works out to approximately 0.145. Not terribly likely, but far from impossible.