Matthew Yglesias, commenting on a man who is in jail for murder despite exculpatory DNA evidence, propounds an interesting theory:

The true limiting factor in determining how many people are in jail is the amount of space available in the jails which, in turn, is limited by the amount of money folks are willing to dedicate to prison construction and maintenance. In practice, if the jury had let this guy off the hook the space he occupied just would’ve been taken up by harsher sentences for several people convicted of lesser crimes like robbery and assault. In crime-reduction terms, the net effect of convicting any particular person — even if he’s guilty — is likely to be zero. Prosecutors would’ve just pushed for tougher sentences in plea bargain negotiations with other offenders, since they would’ve had more beds to fill.

Have there been any studies on the extent to which available jail space factors into prosecution decision-making? I can’t imagine that the correlation is especially high, particularly in cases where the prosecuting attorney is at a different level of jurisdiction than the incarceration facility. Why would, say, a local D.A. care how much room is available in a state penitentiary? For that matter, would have even know? I would think that prosecutors would be inclined to push for the maximum sentence they think they can get in every instance.

Matt also wonders what goes through the minds of juries that convict based on apparently flimsy evidence:

The evidence here isn’t so strong and I do have some doubts that the guy is guilty. But I think he’s probably guilty since I basically trust prosecutors and the police. Moreover, he’s accused of a really awful crime and crime is really awful. We can’t take the risk of letting these people out on the streets or else a bad crime situation in this country will get even worse. So let’s convict, but no death penalty.

This strikes me as quite plausible. I have sat in on a handful of trials, and the type of reasoning Matt suggests was a large thrust of the DA’s closing argument to the jury: “We have a huge problem with drugs/rape/etc. and this guy is charged with that. Drugs/rape/etc. are very, very bad. You must send a message that this community won’t tolerate drugs/rape, etc. If you don’t convict this man, you’re condoning drugs/rape, etc.” That said, in the few trials I’ve watched where I would have voted to acquit, the jury did.

FILED UNDER: Law and the Courts, Policing, ,
James Joyner
About James Joyner
James Joyner is Professor and Department Head of Security Studies at Marine Corps University's Command and Staff College and a nonresident senior fellow at the Scowcroft Center for Strategy and Security at the Atlantic Council. He's a former Army officer and Desert Storm vet. Views expressed here are his own. Follow James on Twitter @DrJJoyner.


  1. You’re probably right on the micro-causal issue here, but I believe prosecutors are aware of the general prison-crowding situation in their jurisdictions. Moreover, regardless of the precise causal links (whether it’s through prosecutors or judges or parole boards or whatever) the fact remains that there’s only so much space in prisons and that this space is, in practice, always filled. The criminal justice system is consistently faced with a massive surplus of sentence-years that could be legitimately applied to offenders relative to the amount of available space. The vast majority of offenders are getting off more lightly than the statutes, if strictly applied, would allow, so if any particular person gets off more lightly than the average, the gap will be made up. The fate of individual offenders has little to do with the aggregate incarceration level.

  2. M. Murcek says:

    In the case of someone wrongly sent to prison or condemned to death and then later exonerated, we should have a legal career death penalty. The judge and prosecutor and jurors involved in a wrongful conviction should all be permanantly removed from any involvement in the legal system. This would include being barred from being a courthouse toilet attendant.

  3. James Joyner says:

    Umm, why? Aside from the catastrophic consequences it would have on the system–both in terms of the risk averseness on the original trial and well as maximum incentive to thwart any attempt to correct the mistake after trial–it’s bizarre to think that most wrongful convictions are the result of malice or incompetence. Most convicted murderers are scumbags; even the ones later proven innocent of that particular crime often had an amazingly checkered history that lent credence to the existing evidence.

  4. Mithras says:

    Wow, James, what an incredibly vicious, liberty-hating thing to write. Why should we be upset if the wrong person goes to jail? Why do you need to even ask this question? The answers are numerous and obvious.

  5. Mithras says:

    One other thing:
    it’s bizarre to think that most wrongful convictions are the result of malice or incompetence…

    As someone who has actually put people in jail, I wish I could impress upon you the pressure to produce a conviction. There is a strong institutional and personal motive to fudge just a little. It doesn’t even seem wrong in the moment. We all know he’s guilty, right? Only, the little “fudges” add up to material evidence, and suddenly someone is being tried on the basis of a tissue of lies.

  6. Xrlq says:

    What exactly is “exculpatory” DNA evidence? A DNA match, unless it can be explained some other way, is extremely damning. But unless the jury relied on their false belief that there was a DNA match, the lack of one proves almost nothing. It’s akin to saying “they never found my fingerprints on the gun, therefore, I can’t possibly be guilty.”

  7. Mithras says:

    Xrlq – the lack of evidence against a defendant is generally considered exculpatory. At least, in the American system.

  8. Paul says:

    In crime-reduction terms, the net effect of convicting any particular person — even if he’s guilty — is likely to be zero.

    heh sounds like that NYTimes headline a while back “Crime rate drops despite harsher sentencing.”

    Good thing there are no logic police or Yglesias would be jailed… DNA or not.

  9. My understanding is that exculpatory DNA evidence is, e.g., a match of semen from a rape or murder/rape victim to DNA from a prison inmate *other* than the guy who is behind bars for having killed/raped her.

    Or: blood left behind at a crime scene that had to belong to the perp for one reason or another (blood-spatter patterns prove this, or the blood is on the window sill where the perp gained entrance). Suddenly the blood is tested against that of the guy who supposedly did the crime years ago–and it ain’t his.

    That kind of thing. I think anyone who wants access to this kind of evidence should get it, and it *should* form the basis for a retrial. Fair’s fair.