local couple has been murdered in their own home. You, a respected
officer of the law, are responsible for tracking down their killer. But
leads are short and public pressure to solve the case is building by the
day. Your career’s on the line here. What do you do?
you were a cop in 17th century France, the answer would have been: find
a guy with a magic stick. Indeed, in 1692 French police enlisted a
peasant named Jacques Aymar-Vernay in the search for the perpetrator of a
double homicide. And it paid off. Aymar-Vernay, who had gained a
national reputation for his claimed ability to use a y-shaped stick, a
“divining rod,” to locate sources of water, claimed his divine branch
had fingered a 19-year-old man with a hunchback as the killer. The man
was tortured to death.
we laugh at our primitive ancestors and their naive belief that a
divining rod -- shown by study after study to be no more reliable than
chance -- could actually be used to track down criminals. But the joke’s
on us: we’re still using those magic sticks, except now they have four
legs and are covered in fur.
In last week’s episode, we highlighted one case out
of Virginia where the reliability of a drug-sniffing dog named “Bono”
was called into question after it was found that, of the 85 times the
dog had signaled there were drugs in a vehicle, drugs were only found 22
times. What we soon figured out, though, is that it wasn’t the fault of
poor Bono but his human handlers, just as it wasn’t the stick that was
at fault for sending a French hunchback to his death.
As researchers at UC Davis observed,
police dogs will often signal that there are drugs in a car not because
there are, but because that’s what they think their handlers want. And
that leads to a lot of false positives. In Australia, one analysis found drug-sniffing dogs (or rather, their handlers) got it wrong 80 percent of the time. And the Chicago Tribunefound that police
dogs were wrong in 56 percent of the cases it analyzed -- and in 73
percent of cases involving Hispanic drivers, indicating that the dogs
are being used to rationalize racial profiling in the war on drugs.
that hasn’t stopped the police from relying on dogs for a simple
reason: like the divining rod of old, the dogs lend a pseudo-scientific
rationale to whatever it is one wants to do, be it finding a suspect to
pin a murder upon or allowing one probable cause to search a vehicle.
Indeed, in the “Bono” case a judge ruled that it
didn’t matter the dog was wrong 74 percent of the time, according to
one news account, because of “other factors, including the dog’s
training and flawless performance during re-certification sessions” --
and, presumably, because ruling the other way would mean throwing out a
whole lot of other cases. And we wouldn’t want something as silly as
scientific evidence to get in the way of a conviction, no matter the