Roosevelt Middle School hosts talk on DNA evidence
Envelopes, bottles, hair roots, cellphones and airbags all have one thing in common, at least for crime investigation experts.
During a discussion Friday at Roosevelt Middle School, two criminalists cited them as among the most helpful tools when it comes to collecting DNA evidence. The students in their audience are currently learning about blood and DNA.
“If you were to take your pen and just make a dot on the paper, and that was the size of a blood stain, that’s all I would need to get a full DNA profile,” said Learden Matthies, a supervising senior criminalist with the Los Angeles County Sheriff’s Department.
Matthies encouraged students to volunteer at the sheriff’s department crime lab when they turn 17 to get a sense for what the job demands.
“So what fluids are present? Blood, saliva, semen, urine, fecal matter...all these things we might be able to get DNA from — another reason for you to come volunteer at the lab so you could see some of this stuff and say, ‘Do I really want to deal with some of this gross stuff all the time?’”
If the answer is yes, she advised the students to major in biology, chemistry or physics, or any combination of the three subjects in college.
Fellow county criminalist Michelle Madrid showed students photos of a crime scene where they applied Luminol, a substance that detects blood stains that otherwise wouldn’t be visible.
Upon applying Luminol, blood, or even bloody footprints, appear as a blue glow.
“It’s helpful in cases ...where you suspect the blood that was there had been cleaned up, because it can detect blood stains that are not visible to our eye,” Madrid said.
The chemical is also helpful years after a bloody crime took place, where the chemical can detect blood stains underneath carpet, on baseboards, sinks, showers, or on clothes that have already been washed, in which case, criminalists are able to pick up a full DNA profile.
For eighth-grade student Aria Tomar, the discussion was fascinating.
“I thought that was really cool and interesting,” she said, adding that once in a while she watches “CSI” with her mom. “I thought it would be similar [to the show], but it’s very different from it.”
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Kelly Corrigan, kelly.corrigan@latimes.com
Twitter: @kellymcorrigan
