GIST: "Shows like
Law and Order and
CSI have taught a generation of Americans that
blood spatters and handwriting analysis are crucial for catching criminals. The reality, says UCLA School of Law dean
Jennifer Mnookin, is that many of these so-called
pattern evidence techniques used in forensic science are faulty and not supported by evidence. In fact, when it comes to wrongful conviction cases
(where new DNA evidence proves that someone was innocent), bad forensic
science is the second most frequent contributing factor, behind only
eyewitness testimony. There are real, and harmful, consequences to forensic science in the courtroom.
The Verge spoke to Mnookin, who recently wrote a paper on
the uncertain future of forensic science,
about how forensic science is different from laboratory research, which
techniques might be credible, and why she’s not optimistic that the
system is going to change anytime soon.
This interview has been lightly edited for clarity.
Many people don’t realize that forensic science
developed separately from laboratory science and is much less credible.
How did that happen?
A lot of these traditional kinds of forensic science
began outside of the university context and outside of any research
framework. They each have an interesting history behind them. For
example, let’s take handwriting identification evidence. Many of the
early handwriting experts actually had previously been either bank
tellers who were in the habit of looking at people’s handwriting to
decide whether to honor checks, or clerks. For a long time, the
profession of being a clerk and writing things down was a sort of
honorable middle-class profession and the advent of the typewriter
changed that and made it much less necessary, and some of these clerks
went on to assert expertise in handwriting and some other techniques. A
lot of the early developments came from police-adjacent policies that
wanted to figure out how to prove things better. There’s nothing wrong
with any of these origin stories, except that they don’t develop in ways
that invite careful scrutiny and scientific study. When you have a
scientific crime detection lab adjacent to law enforcement trying to
figure out how can we better solve cases, you’re not necessarily looking
at how we can test these new techniques and make sure they’re valid. If you have early handwriting examiners advertising their
authority and hoping that lawyers will come to them for help, there may
not be any situation where anyone’s doing careful scrutiny of whether
they can really do what they claim to do. It’s not that anybody was
trying to commit fraud or do something wrong, but these techniques did
develop in ways that didn’t lead to them being tested carefully because
the judges in these early cases didn’t require it. They just say, “you
claim to be an expert? Sure.”
I’m sure that in the realm of forensic science,
there are some forms of pattern evidence that are more credible and less
credible. What are some examples of that?
The Texas Forensic Science
Commission has put a moratorium on bite mark evidence and others have
expressed doubts, but there has not yet been a trial court that has
excluded it from evidence on the grounds of it being insufficiently
reliable, and that’s shocking. On the other hand, fingerprint evidence has been used
since the early 20th century and there was remarkably little serious
study of its accuracy or error rates. That’s begun to change in the wake
of the
2009 National Academy of Sciences
report on forensic science. There has started to be meaningful
evidence. It’s not as substantial as I wish it were, but it exists now
in meaningful quantity and a number of studies are well-done. There’s
pretty clear evidence that fingerprint experts are more accurate than
lay people or novices. There is a craft knowledge. There’s been some accuracy and error rate studies that
show that, while fingerprint experts do make mistakes, those error rates
appear not to be too high in many circumstances. I think fingerprint
evidence carefully expressed and limited does have enough validity that
it deserves to be a brick in the evidentiary wall. I’m not sure it’s
enough to support a conviction without any other evidence.
What are the consequences of all this? I was
surprised at the stat that forensic science is the second most
frequently found contributing factor in certain wrongful conviction
cases. Do we have numbers or a way to quantify what harm has been done?
It’s incredibly hard to get accurate numbers about
wrongful conviction rate. It’s a heck of a lot higher than zero, but we
don’t have any way of assessing it across all cases. That makes it very
challenging to answer the question of how often forensic science
evidence introduced in court is mistaken or erroneous because we don’t
know how many mistakes we’re making overall. That’s not an encouraging recipe for change.
"People have been sounding the alarm about faulty
forensic science for years. Some hope that there will be widespread
change, but you’re less optimistic. Why is that?
I’m not wildly optimistic. In the time since the National
Academy of Sciences report was issued, we really have seen some
important forms of engagement and some modest forms of change. It would
be a mistake not to recognize and even celebrate that. There’s a new
degree of engagement by forensic practitioners, even parts of the law
enforcement community, by scholars, and by some judges to take these
questions seriously. At
the same time, a lot of the changes seem pretty modest and there’s ways
in which many judges are still exhibiting somewhat ostrich-like
behaviors about forensic science and don’t seem interested in or willing
to confront the hard questions that insufficiently validated forms of
evidence raise. Plus, we have no institutional space that has both
authority and broad stakeholder engagement. I don’t believe there’s a
lot of reason to think that we’re going to have a lot of force for
change. This administration’s Justice Department has been less
interested in thinking about these questions than the Obama
administration, and frankly, the Obama administration wasn’t as
interested in taking these questions seriously as I wish they would have
been.
All this is related to my next question. Change
is hard in general, but what are some specific factors that are keeping
the courts from changing?
There are several factors. One is the power of precedent
in legal decision-making. You have these techniques and some have been
around for a long time, and there’s a bunch of judicial opinions that
say they’re admissible and legitimate. They may not be well-reasoned.
They may not be based on a thoughtful examination of the underlying
validity of the science, but there they are. So you have busy trial
court judges making admissibility decisions about techniques that have
been around for a long time and the easy thing to do, no question, is to
preserve the status quo. Given that we have a system that emphasizes precedent,
that’s an even easier thing for judges to do. Many judges have been
reluctant to even hold hearings about the question of adequate
reliability, or some who permit such hearings end up shrugging and
saying, “it could go either way, but we’ve used it for a long time so
it’s good enough.” It probably doesn’t help matters that more judges
with criminal law backgrounds come from the prosecuting side than the
defense side and these techniques feel like they’re in the realm of
common sense. That’s the judicial side. On the forensic science side,
many don’t have any science background. They come to law enforcement and
don’t necessarily have a college degree, either. Now many forensic
departments do require an undergrad science degree, but it’s very rare
to have PhD-level science training, and many forensic scientists are not
themselves scientific researchers, so they’re not well-positioned to
research their own discipline or think about it from a research
perspective. That doesn’t mean they’re not professionals trying to do a
good job, but they’re not well-situated to be engaged in the exercise of
establishing validity or to deeply understand what that requires.
There’s begun to be some spaces within universities looking at these
questions, but still not a lot. So we continue to have a sort of guild mentality with
forensic science, judges who have institutional incentives not to look
deeply, and prosecutors who often tend to have more resources than the
defense attorneys. That’s not an encouraging recipe for change."
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