The Problem With Experts

Earlier this week, Adam Liptak wrote about the downside of allowing opposing litigants to select their own paid experts to render opinions as trial witnesses. He discussed the Australian concept of "hot tubbing," where the litigants' experts "testify together at trial — discussing the case, asking each other questions, responding to inquiries from the judge and the lawyers, finding common ground and sharpening the open issues," and the practice prevalent in Europe, where "expert witnesses are selected by judges and are meant to be neutral and independent."

In criminal cases, as Radley Balko and Roger Koppl discussed in a Slate article yesterday, experts who are paid "charlatans are only half the story." [More ...]

Courts have also missed plenty of mistakes from well-intentioned, conscientious scientists, too. In fact, these may be even more common—and harder to catch. Studies show that crime lab fiber, paint, and body fluid analyses, for example, may consistently have error rates of 10 percent or higher. The error rate in fingerprint analysis is possibly between 1 percent and 4 percent. And bite mark evidence is notoriously unreliable though still widely used.

Most of the forensic evidence in criminal trials comes from government crime labs. We need to demand unbiased, reliable results from forensic scientists even if they are paid by the same government that pays the police and prosecutors.

It's not enough to weed out the incompetent scientists. We need to begin to monitor even the good ones. One major barrier to improving forensic evidence in criminal trials is that in most jurisdictions, the state has a monopoly on experts. Crime lab analysts and medical examiners (and to a lesser extent DNA technicians) typically work for the government and are generally seen as part of the prosecution's "team," much like the police and investigators. Yes, science is science, and it would be nice to believe that scientists will always get at the truth no matter whom they report to. But studies have consistently shown that even conscientious scientists can be affected by cognitive bias.

Experts who slant their testimony to favor the prosecution are difficult to overcome.

Most jurors aren't aware of any of these biases; in fact, most give enormous weight to expert witnesses. Even out-and-out frauds like West and Shaibani can persuade jurors if they're presented in court as reputable experts, appear likeable, and can testify with conviction. A study of the first 86 DNA exonerations garnered by the Innocence Project estimated that faulty forensic science played a role in more than 50 percent of the wrongful convictions.

The linked story suggests several proposed reforms to reduce the risk of a wrongful conviction due to sloppy science.

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    having had some fair share of experience (5.00 / 1) (#3)
    by OldCity on Thu Aug 14, 2008 at 07:52:38 AM EST
    with retaining experts and expert witnesses, I can write confidently that there is no hope of eliminating bias.

    The simple fact of the matter is that in any interpretive discipline, ideology and orientation play a role.  Causative factors, fact patterns, evidence chains, they're all items on which people, even very educated, very qualified people disagree on an academic basis.  when one factors in personal interest and societal bias, it's hard to imagine true objectivity.

    That's why most systems offer each side the opportunity to present their own witnesses.  No question, that system is not perfect and is often more reliant on stratgey than substance, but there's no real way to set up and fund any sort of "double blind" procedure to supplant what is currently utilized.  

    The costs would be horrendous.  Evidence chain, personnel, physical plant, critical path management, remuneration of staff...the mind boggles at any government willing to establish such a structure.

    Very true. (5.00 / 1) (#6)
    by Fabian on Thu Aug 14, 2008 at 08:01:31 AM EST
    High standards are expensive.

    Having had 20 years (5.00 / 1) (#7)
    by ytterby on Thu Aug 14, 2008 at 08:47:20 AM EST
    experience as an expert witness, 75% prosecution, 25% defense, I agree the system needs to be changed. Many experts testify to the paycheck and the camera, not the science. As in any field, there are honorable and not-so-honorable practitioners. As a DA once told me when I testified for the defense after several cases where I testified for the prosecution, "We're OK with having you testify for the defense. We have our list of whores, and you're not one of them."

    Mayor Richard J. Daley: "Experts - (none / 0) (#1)
    by Xanthe on Thu Aug 14, 2008 at 06:16:11 AM EST
    what do they know?"

    Query: why does the criminal defense bar (none / 0) (#2)
    by oculus on Thu Aug 14, 2008 at 07:14:04 AM EST
    readily accept DNA results as establishing "innocence" but question such results in establishing culpablity?

    Because (5.00 / 1) (#8)
    by OldCity on Thu Aug 14, 2008 at 09:34:37 AM EST
    it's their JOB.  Each side advocates for their position.  

    The job of any advocate is to establish a more credible fact pattern.  Often, for the defense, it means putting the credibility of evidence into quesiton.  To not do so would be legal malpractice.  

    The science of DNA really isn't questionable.  However, custody of evidence, methodology, practioners; all of those can be legitimately questioned without debunking the actual science.  That's what most people miss.  DNA analysis, done correctly, is conclusive.  However, if duplicitous persons are involved in the process, it can be perverted, as we've seen.

    The burden on prosecutors is huge.  Despite popular opinion, they don't have a great deal of latitude when it comes to following procedure; we have a horrible habit in America of treating outliers like trends.  In most instances, defective cases get kicked.

    Obviously, the system can be improved.  But, again, to do so will require a huge capital investment which no government will make at this time and also revision of existing civil and criminal procedures (good luck with THAT).


    Because (none / 0) (#4)
    by Redshoes on Thu Aug 14, 2008 at 07:54:51 AM EST
    the state agent or government official may manipulate evidence (DNA or otherwise) or misinterpret in their zeal to catch/convict.    The bias (intentional or otherwise) isn't there if the DNA exonerates.

    DNA is great at excluding (none / 0) (#5)
    by Fabian on Thu Aug 14, 2008 at 07:57:24 AM EST
    a suspect.  The way DNA works is to match one genetic "fingerprint" against another.  It's easy to see if two samples do not match, but it's harder to tell if two match well enough to be conclusive.

    Say you have twenty samples.  In those twenty, seventeen don't match the target sample.  Three might be matches.  How close does a match have to be to be conclusive?  Will there ever be a "perfect match"?


    The defense bar's role (none / 0) (#10)
    by gyrfalcon on Thu Aug 14, 2008 at 09:46:27 AM EST
    in our system, which is absolutely critical, is to do everything possible to force the government to watch its p's and q's, be honest, and not take shortcuts.  Defense attorneys, in my mind, don't so much defend individual accused but stand up for all of us against the too easily corrupted power of the government.

    i've had a number of occassions, (none / 0) (#9)
    by cpinva on Thu Aug 14, 2008 at 09:37:12 AM EST
    over the past 25 years, to deal with "experts". in my experience, most are certainly well qualified, in their respective fields. however, it is impossible for them to be truly independent, any more so than an accounting firm can be, when performing an audit. someone is footing the bill.

    this isn't to suggest an obvious bias on their part, it's mostly subconscious: they want to get hired again.

    as a result, i tend to take all of them with a grain of salt.