Thursday, January 14, 2010

Hobgoblins of Little Minds

The Evidence

The evidence was iffy.

The composite drawing from eyewitnesses looked as much like the co-defendant (who was supposedly out in the getaway car) as it did the guy charged with being the shooter. The witnesses didn't do much better identifying him at a lineup: One said he kinda looked like the guy. Another said she recognized none of themen. A third was sure it was him, which was about all they had.

Except for the gun.

But even that was a problem. The criminalist who did the ballistics comparison wasn't sure he had a match. (We'll ignore the problems with ballistics and other supposed matching by trained lookers.) The most he could say is that the gun was "consistent with" the one that fired the bullet that killed the young woman. The murder weapon.

"Consistent with." What the hell does that mean?

It means "might be." It means "maybe or maybe not." It means "sure it's possible." It means "who knows." All of which is a way of saying that it means not much of anything at all.

"He's not desperately poor." That's consistent with the guy who got laid off from the plant and is struggling to get by on unemployment and food stamps and also with Bill Gates and his billions. It tells you nothing.

The Law

One way of thinking about a trial is by analogy to a tennis game. One side serves the ball, the other tries to hit it back. That's direct examination followed by cross examination. You do that with witness after witness. (Yes, the analogy stinks. Bear with me, it's just the set up for the point.)

Like the tennis match, there are rules about how the trial is to be conducted. Some are mere formalities established by tradition. (As the players used only to wear white, so the judge even today wears a robe which is pretty much always black). Some are grounded in our very sense of how things should be done. (Both sides are supposed to do their best to win but to obey the rules.) Then there are the Rules of Evidence, which are sort of like the lines demarcating the bounds of the court. The ball must not land outside the lines. The evidence must comport with the rules.

One of the basic rules is the rule of relevance. Essentially, what the rule says is that you don't get to hit the ball outside the lines. The Federal Rules of Evidence lay it out.
Rule 401. Definition of "Relevant Evidence"

"Relevant evidence" means evidence having any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence.

Rule 402. Relevant Evidence Generally Admissible; Irrelevant Evidence Inadmissible

All relevant evidence is admissible, except as otherwise provided by the Constitution of the United States, by Act of Congress, by these rules, or by other rules prescribed by the Supreme Court pursuant to statutory authority. Evidence which is not relevant is not admissible.

Got that? If it doesn't make something that matters more or less likely, it isn't relevant and the jury doesn't get to hear it.

Back to The Evidence

So let's go back to that gun. The criminalist's "consistent with" did not indicate that it was likely the gun was the murder weapon. It didn't say there was a 90% chance or a 50% chance or a 10% chance. The criminalist's "consistent with" the murder weapon was really another way of saying, "I don't have any idea whether this gun was or was not the weapon. I might as well never have looked at it." (I know the objection to what I'm saying. I'll get to it.)

But boy did it sound to the jury like he was saying, "Yeah, it was almost certainly the murder weapon, but I can't absolutely swear to it." As I've said before (and in a different context) words matter.

I've been working on a child abuse case. There's really not much question that the abuse occurred, though there's disagreement about exactly what happened and about who did it. The state brought in an expert to opine that the physical evidence was "consistent with" the state's theory of the case being true. The implication, of course, is that the state's theory must be true. In effect, the jury was being told to believe the state.

On cross examination, the expert conceded (grudginly) that the physical evidence was also "consistent with" the state's theory being false. In other words, the physical evidence was, when it was offered, meaningless. It was irrelevant. It was, then, inadmissible.

Oh, you say (and this is the objection I said I'd get to), but it's relevant because a fact, however trivial, that's consistent with guilt makes guilt more probable than a fact that's inconsistent with guilt. Yes and no.

Yes, of course something consistent with guilt makes guilt more probable than something inconsistent with guilt. But that's as an alternative.

If the defense had argued that the gun they found couldn't have been the murder weapon, that it was inconsistent, testimony that it was consistent would surely have been relevant. But by itself, it's nothing.

Some evidence is admissible only in rebuttal. There's a rule, for instance, that allows the introduction of prior hearsay statements that make the same point as live testimony in order to rebut a claim that the live testimony was recently made up. That rule, aptly known as the rule regarding "prior consistent testimony," should probably be the rule about all testimony that A is consistent with B.

It's admissible to rebut a claim that A is not consistent with B, but unless there's some sort of associated quantification, it shouldn't otherwise be admissible at all.

Too damn many people are doing too damned much time based on those claims. The convicted shooter I talked about: Life without parole. The convicted abuser: Life without parole. Are they guilty? The evidence is consistent with guilt.

Of course, it's also consistent with innocence.

Indeed, that is testimony about something being "consistent with" something else.


  1. Yeah I see that a lot as well. Particularly with sexual abuse cases where there is no physical bodily evidence of abuse. The state brings in the medical examiner as an 'expert witness' to testify that the absence of physical evidence is consistent with the abuse having taken place.

    In one case I tried--unsuccesfully of course--to get the expert excluded. In essence the State argues that the absence of A does not mean the absence of B, because everyone would accept that if A is true (evidence of abuse) then B is true (the abuse happened). So I object to the expert on the grounds that 1) no expert is needed to give information about a logically certain syllogism that every rational jury member would, by definition of rational, have to accept; and 2) even if an expert was proper for this type of evidence, the proper expert would be a logician or professor of philosophy, not a medical expert.

    The judge smiled at me as he denied my motion to dismiss.

  2. Think yourself luck that you've got Daubert.

    Over in the UK, Parliament criticised how scientific evidence was treated in our courts. A report was written and subsequently ignored.

    Which lead to criticism in a recent court case, R v Hoey,

    "The House of Commons Science and Technology Committee published on 25 July 2005 the Government's response to the Committee's Report "Forensic Science on Trial" which had been published on 29 March 2005. At paragraph 55 the Committee's comments on validation are repeated together with the Government's response. Both merit reproduction here:

    "55. The absence of an agreed protocol for the validation of scientific techniques prior to their being admitted in court is entirely unsatisfactory. Judges are not well placed to determine scientific validity without input from scientists. We recommend that one of the first tasks of the Forensic Science Advisory Council be to develop a "gate-keeping" test for expert evidence. This should be done in partnership with judges, scientists and other key players in the criminal justice system, and should build on the US Daubert test."

    The Government responded:

    "….the Home Office, ACPO and APA are planning to consult with stakeholders on the issue of quality regulation in forensic science. The establishment of a regulator is one of the options to be considered, as is how the courts can be supported in appropriately weighing scientific evidence."

    When Dr Gill was asked about this in the course of his evidence he said that he did not know whether anything had yet been done by government to further the plan. If it has not then I consider that the evidence given in this case by the FSS witnesses reinforces in the clearest way possible the need for urgent attention to this task for I am not satisfied that the publishing of two journal articles describing a process invented by the authors can be regarded without more as having "validated" that process for the purpose of its being confidently used for evidential purposes.

    Of course, we all know that the problem with Daubert is that it exposes the lack of the probative value of fingerprint evidence. Hence the situation we are in.