In my last post I discussed Convicting the Innocent which discusses how false or misleading forensic evidence contributed in the first 250 DNA exonerations case. It discussed several types of forensic practices and how they can be twisted or how they can be just flat out bad “science.” This week I wanted to talk about some ways the law regulates these possibly unreliable practices and how we can keep lies from coming into our courtrooms.
So, first of all, almost all experts are paid for their testimony by the party who called them, whether they be for the defense or plaintiff. There may be a few good souls who do pro bono (free) work, but this is rare. This should not affect their testimony nor bias them in any way, and it is illegal to pay an expert to give a certain opinion. That being said, we can’t always be sure whether an expert is biased, and further most parties will choose experts who they expect to give a favorable opinion. It is the job of the opposing counsel to obtain testimony about whether the expert is being paid, whether the their payment is biasing their testimony, or whether any other factor is biasing their testimony. If this information isn’t brought out on the stand, the jury will never hear it. For prosecution’s witnesses in particular, many of the analysts called work for law enforcement, which also has the potential to affect their testimony. Analysts do not typically work blind, so if for example a suspect confesses, they may know that when they’re working, giving them an idea of what the “right” conclusion is supposed to be. Again, if this information is not brought out on the stand, the jury will never know whether the information they had about the crime affected their judgement.
The two big court cases that regulate expert testimony are Daubert v. Merrell Dow Pharmaceuticals and Frye v. United States.
In Frye, the court considered the admissibility of a practice called the systolic blood pressure test, which is kind of like a polygraph test. As a result of this case, the court imposed a new burden on expert testimony: it must be “generally accepted” by the relevant scientific community. The big problem with this standard is its vagueness. What counts as generally accepted? Does a majority of the community have to accept it? A large percentage? Does it have to be unchallenged? How much research has to be done on a theory before it counts? But then again, a lot of standards in law are kept vague in order to apply to a variety of cases. Something can sound nice and specific, and then we need to start making a million exceptions because unique situations come up where the standard just doesn’t work. But it also leaves a lot of room for interpretation. It also seemed to contradict Rule 702, which states that if scientific or technical knowledge will help the trier of fact (the judge or the jury) understand the evidence or decide the facts of an issue, a qualified expert may testify. It’s possible Rule 702 could allow a witness to testify, while the Frye standard says the evidence isn’t generally accepted. So which one should a judge prioritize?
Luckily, Daubert created a bit more clarity. First, it clarified that Rule 702 was the decider of admissibility for expert testimony. It also made the judge the “gatekeepers” when it comes to expert testimony relying upon scientific evidence, and they had to decide whether evidence is scientifically reliable. But this left judges confused as to which practices to apply Daubert. This led to the amending of Rule 702, which laid more specific guidelines for applying Daubert and more specific guidelines for what to consider regarding admitting expert testimony. These guidelines aren’t meant for the judge to decide whether an expert’s conclusions are correct, rather whether they were reached used scientifically valid evidence and practices. Unfortunately, judges are not scientists and may not have the knowledge to properly decide when to admit evidence. Therefore, faulty forensic testimony is often still allowed.
This is not meant to be a comprehensive list of every law regarding expert testimony, but these are the major cases that litigate the issue. I’ve also been working hard on my final presentation and product, and I’m very excited to talk about what I’ve learned.