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DNA is just one part of evidence police use to solve crimes

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Posted at 6:47 PM, Sep 24, 2021
and last updated 2021-09-24 22:19:28-04

CORPUS CHRISTI, Texas — Gabby Petito’s case made national headlines while officials searched for her, and when her body was found. Forensics helped identify the key details in her case.

This week is National Forensic Science Week, and Corpus Christi Mayor Paulette Guajardo honored the Corpus Christi Police Department’s crime lab manager Bob May with a plaque last week.

May has worked in forensic science for 20 years, and has been in law enforcement for about 28 years.

He said fingerprints, tire tracks, hair follicles, blood, and bullets can all identify people who have committed crimes.

“Sometimes a single piece of evidence can make the difference in a case," he said. "A single fingerprint can be the difference in convicting somebody or not."

May said his forensics team has several ways of lifting evidence such as fingerprints -- fingerprint powder, but also super glue in a sealed chamber. This makes fingerprints visible on surfaces, helping to solve crimes.

The Corpus Christi Police Department's forensics services division also solves crimes by analyzing guns and their projectiles, such as casings and bullets.

“We are not in the business of convicting people," he said. "We’re in the business of what we find ground truth."

However, the truth can be hard to find. May said that sometimes the DNA samples they collect can have multiple people’s DNA. He said that’s why it’s important to put aside any biases he has when he solves a crime.

“We all have the potential for bias and so that is a challenge for us, because we have to train ourselves to put that aside and look at the evidence in front of us,” he said.

May said forensics isn’t used in all cases. He said if the case has substantial evidence, such as video, then they don’t need forensics to convict someone of a crime.

He said forensics is also often used to exonerate someone of a crime.

The Portland Police Department also uses forensics to solve crimes.

Angela Skoruppa is their crime-scene investigator, and said when it comes to finding a missing person, they use digital evidence like phones or tablets to see where that person was last and who they last talked to.

She said while the strategies to solve something as big as homicide cases vs. burglaries are the same, they do differentiate when it comes to evidence.

“The most difficult part of the job is the amount of items that you can receive, whether it’s something as similar as a found property or going all the way to a homicide, where there’s multiple layers of evidence that needs to be collected and stored and documented,” Skoruppa said.

Both May and Skoruppa said that the kinds of cases they use forensics for the most are property and vehicle theft crimes.