All about Fingerprints and Other Impressions

While footprints made with shoes can be cast and the "moulages," or cast impressions, can be compared on databases, they're not as unique as the prints made by bare feet. That's because not only do the bottoms of the feet have characteristic ridges, but they also have shapes unique to the person...at least according to those who are studying this data.

A three-dimensional footprint impression at a crime scene can be taken from soft surfaces like clay, sand, and snow. It's photographed and then cast with dental stone or silicone casting material. The impression is first stabilized with a spray. Then it's powdered to allow easy lifting and a steel frame keeps the casting material contained. It's fully hardened before being examined.

Before 1999, however, the main problem was the lack of a database against which to make comparisons. Then the Royal Canadian Mounted Police invited thousands of people to participate in making one. Foot impression expert Sergeant Robert Kennedy asked volunteers to place their feet onto an inkless pad and then press them on specially treated paper. His hope was to collect as many as twenty thousand samples the first year.

The idea of "barefoot morphology" is based on the belief that individuals have unique patterns to the weight-bearing part of the foot. Research indicates that no two people have the same foot shape, but the database must be substantially increased to give this claim a scientific basis.

And as with fingerprints, an identifiable impression would not convict; it would only contribute to the overall case and assist with leads. Even Richard Allen Davis was not convicted by his palm print but by fibers, a beard hair, the print, his confession, and convincing circumstantial evidence.

What all of this means is that technology developed to locate and preserve impressions made by different parts of the human body is getting increasingly sophisticated. Crimes that years ago went unsolved are now being scrutinized in new ways, and the results might surprise a few criminals. Fingerprint identification is here to stay, and will certainly continue to be improved, but other body parts may also eventually have their day in court.