Every contact leaves a trace. You enter an environment and leave something, taking something away with you when you leave.
That is Locard’s Exchange Principle and the expertise of the crime lab’s Trace Evidence Section, led by Chief Criminalist Supervisor Patrick Jones.
“You may have mud on the bottom of your shoe, and you walk into a home, and you leave that mud there,” Jones explained. “You also potentially leave with carpet fibers on the bottom of your shoe.”
Using a variety of instruments – x-rays, electronic beams, microscopes, and more – the four trace evidence technicians in the crime lab help detectives advance their cases. With Jones, they might determine if they’re dealing with a nylon fiber versus a rayon fiber, architectural paint or automotive paint.
For example, in a hit-and-run crash, crime scene technicians might collect the pants from a pedestrian victim that have traces of paint on them. The paint samples would go into a database in search of a match.
“I can enter the chemical characteristics of the paint I find on the victim’s clothing and potentially generate a hit list of the vehicles that the paint could have come from,” Jones said.
The hit list might be concise, revealing a specific year, make, and model of a vehicle. Or it could be more challenging, providing many years’ worth of a manufacturer’s vehicle make.
All of the trace evidence technicians at KCPD have chemistry degrees, including Jones who graduated from the University of Missouri-Kansas City (UMKC). Jones grew up in the KC metro area with a strong interest in science. He considered being a medical examiner, but ultimately liked the idea of being more of a lab scientist. As a supervisor in the crime lab, Jones accepts the challenge and responsibility of following the science to what may be life-altering conclusions.
“You can have a positive impact in someone’s life doing quality work, examining a case thoroughly, examining a case unbiased and truthfully,” Jones said.
For anyone interested in working in forensic science, Jones says it’s a wide field that covers DNA and fingerprints, document examination, computer technology, and so forth. He recommends contacting your local crime lab for a tour. When it comes to trace evidence, Jones says technicians need to be creative thinkers.
“You might work a glass case one day and a fiber case the next day using different instruments,” Jones said. “One case could have glass, tape, fibers, human hairs, all that, and you have to shift gears. You have to be very patient.”