30.4.2012science

Behind The Scenes

The methods of identifying a killer are as numerous as the methods of killing a person, but how reliable are they really?

The Guardian published a great breakdown of what goes on at a crime scene last week. Using a crime scene from 2001, where a bag containing the dismembered corpse of a 31 year old woman was found at the bottom of a canal, as a case study, we get quotes from all the main players on the scene: the crime scene manager, the police diver, the forensic specialist, the detective, and the documents examiner, who has one particularly impressive tool in their arsenal:

There is the Electrostatic Detection Apparatus – you put a document on it and it produces a vacuum, drawing the document down. We put what I would liken to clingfilm over the top and run an electric bar over it, which charges it – the indented impressions will be a different charge. Over this we pour glass beads with a carbon-based powder on them. The powder sticks and reveals the indented impression: words appear, images appear. It’s like magic. What you then see is often some sort of malicious communication – perhaps a threat sent to the prime minister. Something has emerged out of nothing.

The Guardian also went behind the scenes at LGC Forensics, Britain’s biggest supplier of outsourced forensic science services, earlier this year. LGC employees, they tell us, helped find the evidence used to convict numerous high profile murderers, including those of Damilola Taylor, Milly Dowler, and Stephen Lawrence.

Because the thing about DNA evidence, strong as it is, large as it looms in the public’s imagination, is that it connects a human and an object. It doesn’t prove when the two came into contact. Nor does it necessarily prove they were actually in direct contact at all.

"It’s not just the finding of the evidence," says Ros Hammond, a senior scientific adviser who has worked on many high-profile cases. "It’s how did it get there, and can we rule out any other way it did so? And what does it mean?"

One technique that’s been used to answer those questions is criminal profiling. Malcolm Gladwell wrote about the advent of criminal profiling for the New Yorker in 2007. The technique was born in the 1970s:

Douglas and Ressler wanted to know whether there was a pattern that connected a killer’s life and personality with the nature of his crimes. They were looking for what psychologists would call a homology, an agreement between character and action, and, after comparing what they learned from the killers with what they already knew about the characteristics of their murders, they became convinced that they’d found one.

Serial killers, they concluded, fall into one of two categories. Some crime scenes show evidence of logic and planning. The victim has been hunted and selected, in order to fulfill a specific fantasy. The recruitment of the victim might involve a ruse or a con. The perpetrator maintains control throughout the offense. He takes his time with the victim, carefully enacting his fantasies. He is adaptable and mobile. He almost never leaves a weapon behind. He meticulously conceals the body. Douglas and Ressler, in their respective books, call that kind of crime “organized.”

Profiling enjoyed a great reputation for years, especially on TV shows, but it’s seen some controversy. Anecdotes abound in Gladwell’s story of false convictions and astonishing leaps of judgment, and the science behind it may not even be particularly solid:

Not long ago, a group of psychologists at the University of Liverpool decided to test the F.B.I.’s assumptions. First, they made a list of crime-scene characteristics generally considered to show organization: perhaps the victim was alive during the sex acts, or the body was posed in a certain way, or the murder weapon was missing, or the body was concealed, or torture and restraints were involved. Then they made a list of characteristics showing disorganization: perhaps the victim was beaten, the body was left in an isolated spot, the victim’s belongings were scattered, or the murder weapon was improvised.

If the F.B.I. was right, they reasoned, the crime-scene details on each of those two lists should “co-occur”—that is, if you see one or more organized traits in a crime, there should be a reasonably high probability of seeing other organized traits. When they looked at a sample of a hundred serial crimes, however, they couldn’t find any support for the F.B.I.’s distinction. Crimes don’t fall into one camp or the other. It turns out that they’re almost always a mixture of a few key organized traits and a random array of disorganized traits. Laurence Alison, one of the leaders of the Liverpool group and the author of “The Forensic Psychologist’s Casebook,” told me, “The whole business is a lot more complicated than the F.B.I. imagines.”

These days, forensic testing is a safer bet in securing a conviction and good ratings for your crime drama, but it’s not without its flaws. Texas Monthly reported on Keith Pikett, the “master of the dog-scent lineup,” last year. Pikett helped identify more than one thousand suspects using his scent test, and various other states have used the test, but there’s very little science confirming its efficacy. Moreover, Pikett had no forensic training, and his techniques turned out to be fairly primitive.

The truth is, police and prosecutors have been using questionable forensic techniques for years, things involving bite marks, blood-spatter patterns, and even ear and lip prints. They use them because they help solve crimes. But over the past decade we’ve begun to understand just how unscientific forensic science can be. In the lab and at the crime scene, unsound techniques have incriminated the wrong person time and again. The most visible evidence of this is the 252 DNA exonerations nationwide since 1989—many of which, according to the Innocence Project, involved some form of improper or faulty forensic science. And these exonerees were the ones whose stories had happy endings, saved by DNA taken from old crime-scene samples that had not been discarded; no one knows how many unlucky people convicted on faulty science still languish in prison.

If the Innocence Project sounds familiar, it’s because they’ve been cleaning up the mess of wrongful convictions for years. It came out just this year that the Innocence Project has evidence exonerating dozens of men in Virginia alone using DNA tests (which the state is desperately trying to keep under wraps), and you can look to Texas for even more tales of exoneration due to faulty evidence.

There’s also a sort of corollary to this overreliance on techniques we don’t really understand and have barely tested. It’s called The CSI Effect:

Bernard Knight, formerly one of Britain’s chief pathologists, said that because of television crime dramas, jurors today expect more categorical proof than forensic science is capable of delivering.

Hopefully the inspiration for the name is obvious.

The uncontested kingpin of unreliable convictions, though, is the lie detector:

The county prosecutors offered Buzz a deal: they would drop all charges if he agreed to take a polygraph – a lie detector test – to prove his innocence. Convinced the whole episode was one big mistake, Buzz readily agreed. He took two tests but both suggested he was lying about his innocence. This, along with circumstantial evidence, sealed his 1979 conviction and he spent two-and-a-half years in prison for a murder he didn’t commit.

During his time in prison, Buzz studied the polygraph. He sent his results to a number of experts but received wildly different interpretations. Determined to show the test was fallible, he developed a training exercise to help people fool the lie detector and after just 15 minutes of instruction, 23 out of 27 inmates beat the polygraph. Buzz was eventually exonerated, helped by the testimony of the real killer’s mother, and his case has become one of the most notorious episodes in the history of the technology.

If you agree to a lie detector test, you might as well seal your own confession, but even the simple act of confession can be unreliable:

If you have never been tortured, or locked up and verbally threatened, you may find it hard to believe that anyone would confess to something he had not done. Intuition holds that the innocent do not make false confessions. What on earth could be the motive? To stop the abuse? To curry favor with the interrogator? To follow some fragile thread of imaginary hope that cooperation will bring freedom?

Here are some more stories that go behind the crime scene.

  • If CSI turned everybody into forensic scientists, then Lie to Me made everybody an expert on reading micro-expressions. Surprisingly, though, the science is pretty good. I don’t know how widely this is applied to crimes, but apparently there’s a lot to learn from Mike Daisey.
  • Wildlife investigators at Yellowstone used some of the same crime scene techniques we use for human crimes to catch a killer grizzly bear last year.
  • The Monster of Florence is the name given to the person or persons behind a series of Italian murders in the 60s and 80s. Arrests have been made, but most people think the real killers were never identified. The investigation began with a “spectacularly incompetent” crime scene examination.
  • In The Neverending Nightmare of Amanda Knox, Nathaniel Rich recounts the Amanda Knox case that consumed the media for months. She was coerced into giving a false confession to a crime she may not even have been a suspect in but for incompetent Italian police trampling all over the crime scene.