MINNEAPOLIS (WCCO) — From the time of Sherlock Holmes, trace evidence found at crime scenes has been “elementary” in solving the “whodunit.”
A century later, technology is taking shoe print evidence to a whole new level.READ MORE: With Derek Chauvin's Trial Approaching, Protesters March Through Downtown Minneapolis
Catherine Knutson is Lab Director at the Minnesota Bureau of Criminal Apprehension in St. Paul. She says while DNA analysis grabs the headlines, it is often the trace evidence like shoe imprints that makes a case.
“It’s really what one might consider more of the traditional forensic science,” Knutson said. “It’s actually one of the few disciplines that we not only use on the tail end in order to do an identification and to get evidence into court, but it’s also extremely, extremely valuable on the front end of an investigation.”
When an imprint is discovered, it is photographed to scale. Many times a solid cast is made into a three-dimensional model.
“Sometimes the cast will pick up details that the photo won’t and vice versa, so it’s really good to have both,” BCA Trace Evidence Supervisor Sue Gross said.
But here is where it gets interesting, as those patterned lines — unique to a shoe’s sole — get analyzed in the lab.
“More lines, an X, and now this tread pattern, these things that we’re seeing — we can enter those into the database,” Gross said.READ MORE: No Injuries After Train Derailment In Plymouth
A year and a half ago, the BCA acquired the services of a national database called “SICAR.” It has some 30,000 shoe patterns.
When the print from the crime scene is entered, the computer identifies the brand, model and date of production – and even photos of the whole shoe.
“When a shoe is made, there’s no wear, and it’s brand new. And as a person wears a shoe and uses it, you get wear on it and you get individual characteristics, randomly acquired characteristics,” Gross said.
If there are enough imperfections, lab techs can match a suspect’s shoe to the crime scene. Known shoes are also inked, and the transparency compared to the evidence.
“So now we’ve got this known impression that we can compare to our unknown,” Gross said.
The technology has already helped solve several recent crimes, including a gruesome homicide in St. Paul, the burglary of a bakery and paint store in Eagan and the robbery of a Chipotle in Apple Valley.
“And that’s really the future of many of these databases is to continue and use the power of computers to assist us in our analyses,” Knutson said.MORE NEWS: George Floyd's Cause Of Death, Derek Chauvin's Force Will Be Keys At Trial
The database has produced five positive hits to help local investigators with their cases in the past 18 months.