All about Fingerprints and Other Impressions
The Value of a Database
When 12-year-old Polly Klaas was kidnapped in October of 1993, at first it looked like there would be little useful evidence, but FBI investigators got a break, and it wasn't a fingerprint. David Fisher tells the story in Hard Evidence.
Polly invited two girlfriends over for a pajama party in her home in Petaluma, California. The girls played quietly in her room while her mother was asleep in the next bedroom. Around 10:00 p.m., they were shocked to see a large man wearing a yellow bandana and smelling of alcohol come in through the open window. He threatened them with a knife so they moved quickly to obey him.
First he bound Polly's friends and put pillowcases over their heads. Then he carried Polly off into the night.
The young girls were stunned, but they managed to free themselves and call 911. They described the man to the operator. Then they alerted Polly's mother, who could not believe that such a thing could happen in their quiet neighborhood.
The police arrived and searched the room, but found nothing useful. According to the FBI government web site, they called in the special evidence response team from the FBI office in San Francisco. The crime scene investigators used special alternative light sources and fluorescent powder to locate a few fibers and an otherwise invisible palm print on a rail of the bunk bed in the room. That would help, but they also needed a good description from the girls.
These two frightened girls did their best to supply police sketch artist Ralph Pata with enough details for a composite drawing, so that a "wanted" poster could be made and distributed throughout the state. Unfortunately, despite a massive effort, Polly's abductor was not immediately caught.
About six weeks later, torn children's clothing was found on a hill, near a site where patrolmen had helped a man free his car from a ditch. That man was Richard Allen Davis, who had been convicted of kidnapping twice before and was currently on parole. A fingerprint expert matched the palm print to Davis, and since the sketch matched his mug shots, it helped to narrow the search and close in on him. He confessed to killing the girl and showed police where he'd put the body.
In June 1996, he was convicted of eight criminal counts, including kidnapping and first-degree murder. The jury sentenced him to death.
With the advent of "Livescan" fingerprinting, in which prints are taken with a computerized digital device rather than from rolling the fingertips in ink, some people are concerned that the palm print database will suffer. It appears that agencies around the country are dispensing with the ink process due to the ease of computerized fingerprint readings, even though palm prints have eight to ten times more minutiae than fingerprints. Without access to a large database, some cases may go unsolved. In fact, according to Ruth Kanable's research for Law Enforcement Technology, 25 to 30 percent of the impressions processed at an impression-heavy crime scene are going to be palm prints.
To address this need, Livescan technology is working on palm print scanners. Since the human palm is oddly shaped, they're developing platens that will correspond to the many contours, but it's still a fact that palm prints requite more storage capacity than fingerprints, and the technology will add considerable expense.
In the Klaas case, the discovery of a palm print made all the difference between a killer getting away or getting the death penalty. In another California case, it came down to a facial impression.