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The notorious gangster John Dillinger once paid a doctor to have his fingerprints burned off with acid. The procedure worked, but only for about a month before the fingerprints grew back.

It was just one of the interesting facts that kids learned about Monday at the “Tracks and Traces” program at the North Branch Community Center.

Around 30 kids attended the free program, sponsored by the North Branch Friends of the Library.

The program was presented by the Science Museum of Minnesota and included a demonstration about what forensic scientists can use for clues to figure out a mystery.

The kids first learned about tracks. “Not only do animals leave tracks, but people leave tracks wherever they go too,” presenter Jeff McLennan said.

He showed how tracks like footprints along with other evidence left behind such as fingerprints, fiber samples, DNA and tire tracks can be helpful when police or scientists are trying to solve a mystery.

“Three things that every forensic scientist does with clues are discover, analyze and interpret,” McLennan said.

The kids seemed amazed when he showed them how a fingerprint sample can first be dusted using volcanic ash and then lifted off the surface with a piece of clear tape.

Fingerprints are perhaps one of the most valuable clues that scientists can use at a scene, he said. “No two fingerprints are the same,” he said. “Everyone has their own unique fingerprints.”

McLennan also showed the kids a short video to illustrate how eyewitness accounts of a scene cannot always be reliable.

He asked the kids to count how many times they saw a basketball being passed between players. Then, he replayed the video and told them not to count the passes.

When they watched again, they saw a girl walk straight through the middle of the basketball game.

“Nobody saw her there the first time because you were concentrating on the basketball,” McLennan said. “We can’t always rely on what people think they saw.”

McLennan said forensics also uses photographs, chemical testing, handwriting samples and tool marks to try and solve a mystery.

After the presentation, the kids were able to visit various stations set up for hands-on experiments in forensic science.

At one station, the kids used sticky tape to pick up samples somewhere in the room and then look at their findings under a microscope.

At another station, they were able to record their own fingerprints to take home with them. Other stations had the kids matching shoes with shoeprints and animal tracks with the correct animals.

The program also included door prizes of games and a book given out before the presentation.

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