June 10, 2022

Forensic science student develops “sandblasting” technique to detect fingerprints

“Dust off fingerprints” is a household term for fans of mystery novels and TV shows. But if the University of Toronto Bethany Krebs In its own way, forensic teams will soon be “sandblasting for fingerprints” instead.

The fourth-year forensic science student at the University of Toronto in Mississauga conducted experiments showing that abrasive stripping of a specialized powder from a surface is more effective at revealing fingerprints than the conventional dusting method .

His study, which is part of an advanced independent project course, also found that the innovative method was more efficient and economical.

“This has the potential to be a viable alternative to fingerprint detection, especially with larger crime scenes where there are time and resource constraints,” said Krebs, who this spring finishes a double. major in forensic medicine and criminology.

Detecting fingerprints at a crime scene typically involves using a small makeup brush made of soft camel hair, fiberglass hair, or feathers to gently apply a fine powder to a hard surface. The powder is typically made from aluminum, chalk, bronze, graphite, or iron, and often contains fluorescence to provide strong contrast in the resulting fingerprints. The powder adheres to any trace of sweat, oil, or other natural skin fluid in latent indentations (not visible to the naked eye), revealing a pattern of ridges and furrows unique to each person’s fingers.

While the approach is technically efficient, it is painstaking work that requires a methodical pace in order to avoid damaging the delicate fingerprint residue. Consequently, it can be lengthy when carried out over large areas, which defeats the need for speed which tends to conduct criminal investigations.

“One of the biggest issues is time,” says Krebs, who has already completed two years of undergraduate studies in criminology at Wilfrid Laurier University. “If you have a large and complicated crime scene, cleaning the areas for fingerprints can be time consuming.

“Also, if the brush is too stiff, or if you apply too much pressure, or if the powder is not evenly distributed on the brush, it can damage fingerprints.”

With the advice of a forensic identification instructor Wade knapp and laboratory technician Agate Gapinska-Serwin, Krebs set out to find a less invasive and more efficient method. First, she obtained samples of six substrates commonly found in homes: painted drywall, galvanized steel, treated hardwood, ceramic tile, laminate countertop, and glass. She then asked two friends to touch the substrates, resulting in a total of 144 fingerprints.

A gravity-fed sandblasting gun powered by an air compressor is used to spray fluorescent yellow cornstarch powder (photo by Bethany Krebs)

His research took place in early February at the Crime Scene House, a campus where forensic science investigative and documentation techniques are practiced. There, she used a gravity blast gun powered by an air compressor to spray fluorescent yellow cornstarch powder onto each sample. Cornstarch is a proven fingerprint developing substance that is much more affordable and readily available than regular fingerprint powder. It is also less toxic, making it safer for aerosol application.

“It comes in the form of a cloud – it’s just settling on the fingerprints rather than being applied manually. It’s completely non-contact, which means there’s much less chance of damaging prints, ”says Krebs.

She then photographed the fingerprints that appeared and assessed her findings. With this method, 100 of the fingerprints were fully developed and 10 were heavily developed – in both cases providing enough detail to allow precise identification. The results correspond to a success rate of 76%. Krebs is now exploring opportunities to officially publish his research.

The study’s completion confirmed to Krebs what she loves most about forensics: the ability to apply scientific knowledge to help solve crimes.

“Making a difference in the lives of individuals by finding the truth is what motivates me,” she says.