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Visual hair matching has resulted in many criminal convictions. Science says it's bogus

Anyone who has watched shows like “CSI” or “Law & Order” knows that police sometimes use hair from crime scenes to try to track down a suspect. But the National Registry of Exonerations found more than 100 cases in which suspects were convicted, at least in part, because of flawed hair analysis or testimony.

Rene Ebersole is an independent journalist writing about science, health and environment. In a piece for the Marshall Project, she delves into some of the scientific problems with hair analysis — and how both victims’ rights groups and law enforcement are reacting.

The Show spoke with her and asked what got her started with this story about the fact that hair analysis as it relates to forensics is maybe not as reliable as some people think it is.

Full interview

RENE EBERSOLE: It’s kind of a funny story. As I’m sure you know from covering a lot of things, one story often leads to the next. And a couple years ago, I was at the University of Tennessee Body Farm. I was doing a story on the science of human decay, and I was talking to some forensic anthropologist there about trustworthy science being admitted into courtrooms and how new techniques have to go through a lot of vetting and testing before they can be admitted.

And then we started talking about all these other types of science that have been long accepted — and we’ve seen them in all the crime shows — but many of them have been discredited in recent years: like blood spatter patterns, arson analysis, bite mark comparison. And microscopic hair comparison was one of the ones that they mentioned.

And I became really intrigued with that topic because I didn’t really realize until I started reading that hair comparison — visually hair matching one hair to another, one hair from a suspect to a hair at a crime scene — it’s been debunked for a very long time. For like two decades. But there’s still a lot of people in prison based on that evidence.

MARK BRODIE: Why is that? It seems like maybe our prosecutors are just not not real keen to let go of some of those cases. Or are people just not aware of the fact that this is maybe not as reliable as people think it is?

EBERSOLE: The thing is, whenever a type of science is discredited, cases are not automatically reopened. The onus is really on the inmate and their attorneys to study up and be aware of what’s going on and then challenge the science if they believe that the science has been used to wrongfully convict them.

But hair evidence at crime scenes is everywhere. The average human head alone contains as many as 120,000 hairs, and we lose about 100 per day. So our hair’s falling out, and it’s getting on people’s clothing and all over the room. So there’s always a lot of hair evidence at a scene.

It’s often something used in these particularly heinous crimes — you know, rapes and murders. It’s often a piece of evidence that’s used for that. And today it’s supposed to be backed up with DNA. If they visually match two hairs and they say these look very very similar, then it should be checked with DNA evidence. But that type of science really didn’t exist until the late 1990s.

BRODIE: That’s one of the things I found so interesting about your reporting, which is that the hair analysis is really kind of a visual thing, right? Somebody looks at it and says, “Yes, this looks like another sample of a hair that was taken from this suspect’s body,” or it doesn’t. And it seems like it doesn’t really get much more scientific than that.

EBERSOLE: No. There were about there were more than a dozen characteristics they would purportedly look at. And some of them were as simple as the color of the hair, whether it looked like it was cut or if it had fallen out. They’d look for visual characteristics that were pretty obvious.

But then there were others that were a little bit less scientific. … The funny thing is, none of these types of science were ever developed by academics like what happens today. They were developed by police who were just trying to do good police work, trying to figure out how to connect suspects to crime scenes. But they haven’t really held up. Many of them haven’t held up very well.

BRODIE: Are there organized efforts to try to re-look at cases of people who were convicted based on this kind of evidence?

EBERSOLE: Yes. There was a federal review of, I think it was about 2000 cases that underwent a federal review. And there have since been about 17 states who have looked at cases, and those states have done reviews.

But it’s very expensive. A lot of times they don’t have the resources to do these reviews. A lot of times it takes people really pushing.

The National Innocence Project and Innocence Projects in the state level have done a lot of work to try to get these reviews done.

BRODIE: Are prosecutors still using hair samples as evidence in their cases, or is this the kind of thing that mostly has gone by the wayside and we’re just looking at cases that have already been prosecuted?

EBERSOLE: Hair is still used all the time, and they do still use microscopic hair analysis to visually match, to visually detect whether there’s a difference. But then it has to or it’s supposed to always go through DNA analysis if they find two hairs appear to match.

BRODIE: Well, is there a problem with that? I mean, if they’re if they’re not using it as the (only) tool but using it as a tool and then sort of trying to corroborate or exonerate based on more scientific DNA evidence, is that a problem?

EBERSOLE: The people I’ve interviewed, most of them have said they don’t have a problem with it as a screening tool, as long as it’s only used as a screening tool. DNA tests are expensive, and it would be easy to say, “Oh, well, we’re pretty sure that’s, you know, let’s save the money.”

And the time. A lot of times it takes a lot of time to get this test done, so hopefully they’re being done.

BRODIE: As you say, a number of these tools that that law enforcement had used to try to tie potential suspects to crimes have been discredited. Are there new methods that are coming in to take their place? If you’re not using hair, if you’re not using blood splatter, if you’re not using bite marks, for example, are there other things that law enforcement is able to use that are maybe more reliable?

EBERSOLE: DNA is considered the gold standard. There was a National Academy of Sciences report a number of years ago, and, basically it was determined that the DNA analysis is really the only type of individual identification that can be trusted. And even with that, there are often issues with DNA. But DNA is really the only one that’s very reliable.

And in terms of new scientific techniques, there are I think there are a lot of new things in development. That story that I was working on before had to do with using the necrobiome — the way the microbes are drawn to the body as they decay — to try to figure out time of death.

There are some new techniques that are up and coming, but they have to be tested and vetted and then accepted in court before they can be used widely in cases.

Mark Brodie is a co-host of The Show, KJZZ’s locally produced news magazine. Since starting at KJZZ in 2002, Brodie has been a host, reporter and producer, including several years covering the Arizona Legislature, based at the Capitol.