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Sep 01, 2023

Proof in the paint leading to breaks in criminal cases

by: Michelle Wolf Posted: Aug 10, 2023 / 06:12 PM EDT Updated: Aug 11, 2023 / 08:42 PM EDT NORFOLK, Va. (WAVY) — Technology is leading to big breaks in cases with very small pieces of evidence. It has

by: Michelle Wolf

Posted: Aug 10, 2023 / 06:12 PM EDT

Updated: Aug 11, 2023 / 08:42 PM EDT

NORFOLK, Va. (WAVY) — Technology is leading to big breaks in cases with very small pieces of evidence. It has already helped in a deadly hit-and-run in James City County.

Sixty-four-year-old Andrew Davis was walking his dog when he was hit and left for dead. State police had no leads but now a vital piece of new information could change that.

Virginia State Police sent evidence samples to the Department of Forensic Science. With paint chips smaller than the point of a pencil, forensic scientists can determine the make and model of a vehicle.

“This can be a time consuming process,” said Brenda Christy, trace evidence supervisor at the Virginia Department of Forensic Science laboratory in Norfolk.

It’s a time-consuming process, but one that Christy said is highly rewarding.

“It’s very rewarding when they find the car,” Christy said.

She’s spent the last two decades working in forensics.

The process starts with scraping articles of clothing and collecting the particles that fall off to view under a microscope.

“We’ll suspend the clothing on these hooks,” Christy said. “Generally we’re trying to make anything that’s adhered to the clothes fall off and then we’ll collect it onto a piece of white paper into a tin. We’re collecting between a tablespoon and as much as half a cup of dirt and debris and dried blood, body fluids, and hopefully some paint.”

Christy then separates the debris into multiple tins and searches for pieces of paint, which is successful about 50% of the time.

“Moving everything around with tweezers to make sure that we make them flip over to see if there’s anything in there that is paint,” Christy said while demonstrating the technique.

If a particle is found, it’s recorded under a microscope and then an FTIR, or Fourier Transform Infrared Spectrometer.

“It sees how each of these layers of paint work, because we’re going to analyze them, individually, how it’s going to absorb infrared light,” Christy said. “As it absorbs light, it gives us information about the chemicals or the compounds that compose each of those layers.”

The wave form the paint particle generates is entered into the PDQ, or paint data query database. The database contains paint composition information on more than 25,000 vehicles, going as far back as the 1960s.

“There’s paint samples in the database that go back to the 1960s but its most populated from 1990, forward,” Christy said.

The PDQ was originally created in partnership with the FBI and Royal Canadian Mounted Police.

“It’s only available to law enforcement, and we have to provide the RCMP with 60 paint samples a year,” Christy said. “We’re looking for the plant of origin, primarily looking at the clear coat and the primer layers. The color of the vehicle is the last thing we’re going to look at in the entire search.”

The chemical composition of those layers can give scientists like Christy enough information to find the factory a car was manufactured at, the year or year range and a potential model. While Christy said there will never be a complete match, they can get pretty close and the process from scraping clothing to the PDQ can take a few days to a week.

“We look for the car’s cousins in the database because it’s not that car, we’re looking at something else that was made at that factory at that time,” Christy said.

The information is shared with police and a suspect, Christy said, is caught in about 25% of cases.

In Davis’ case, a paint particle determined the suspect vehicle to be a black to dark gray Honda from 1995-2015. The car has significant front-end damage.

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