Biology Reference
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solely or partially on his false testimony, according to the Innocence Project. Preston claimed
what tracking-dog experts say is impossible—that his dog could smell human traces months
or even years after a suspect walked over the ground or on heavily trafficked streets. One
man was freed in 2009 after spending twenty-six years in prison. Florida prosecutors hadn't
bothered reviewing Preston's cases after he was exposed as a fraud in the mid-1980s. In 2008,
Florida State Attorney Norman Wolfinger ordered a review of murder and sexual battery cases
where Preston testified, although the local newspaper editorialized that an independent in-
vestigation was needed. That didn't happen. Preston died in 2008.
Keith Pikett, a now-retired Fort Bend County, Texas, sheriff's deputy, is a more recent,
still-living legend. His claims about his bloodhounds' scenting abilities resulted in what the
Texas Innocence Project told the
New York Times
amounts to fifteen to twenty people in pris-
on “based on virtually nothing but Pikett's testimony.”
Pikett had been involved in helping indict more than 1,000 suspects nationwide. His spe-
cialty was the scent lineup. A scent lineup starts with collecting scent from a crime scene,
then collecting scent from a suspect. The dog's job is to “match” the scent from the crime
scene with the scent of the suspect. For scent matching to be valid, it needs to be done un-
der pristine circumstances, double-blind, with careful preservation methods. In the Nether-
lands—where the courts accept scent lineup but only as corroborating evidence—they use
more than one dog, and the work is done in a sterile room without handlers present. In other
words, no cross-contamination and no possibility of Clever Hans. That's not the way Keith
Pikett did it in Texas.
Ultimately, the police evidence videos showing Pikett and his dogs running scent lineups
“cooked him,” Roger said succinctly. I watched them online. Paint cans with numbers were
placed on the grass in a line. An investigator pulled gauze pads in plastic bags out of one can
and put them in another with bare hands. If there ever were an uncontaminated scent object
with the suspect's scent on it, that scent was now possibly in several cans. Pikett then ran his
bloodhounds on leashes down the line of paint cans. The dogs would look up, bay, stop when
Pikett stopped. They would shake their heads, slobber flying, and bay again. They avoided
some of the cans. Pikett stopped one dog at a can with the leash, and the dog stood there.
Another dog paused squarely between two cans, and Pikett said the dog had alerted on one
of them. One dog bayed and ran past two cans, and Pikett said the dog had alerted on one of
them. Head shakes, barks, and pauses were all alerts, according to Pikett. The bloodhounds
were doing all three of those things.
“This is the most primitive evidential police procedure I have ever witnessed,” Robert
Coote, the former head of a British K9 police unit, testified after he watched the videos. “If
it was not for the fact that it is a serious matter, I could have been watching a comedy.”
