Behind-the-scenes at Bexar County Crime Lab: Thousands of guns, ammunition part of criminal investigations

Firearms section has analyzed estimated 2,500 items of evidence this year

SAN ANTONIO – Forensic scientists are getting hands-on with guns and bullets inside the firearms section at the Bexar County Crime Lab.

The firearms lab gets thousands of guns and ammunition each year to assist criminal investigations.

Holli Worden and the team test firearms, cartridges and bullet casings collected from crime scenes or items confiscated by law enforcement officials.

“Every firearm leaves its own pattern of tool marks, and this pattern is different at the microscopic level,” said Holli Worden, a forensic scientist at the Bexar County Crime Lab. “We’re looking at two elements. One would be the fired cartridge case, and one would be the bullet. The bullet itself is going to pass through the barrel. Every barrel is going to leave its own pattern of tool marks on it.”

Worden said every firearm and bullet is unique, like a fingerprint. It’s the scientists’ job to determine how and if they were used during a shooting.

Some of the tools used during their investigation include a large water tank used by scientists to shoot and retrieve bullets. The lab also has an ammunition and firearms reference collection room. It’s essentially a large database used for comparison.

“Everything we receive is essentially to determine if that specific gun was used in that crime. If there’s a firearm seized from a crime scene, or from suspects, or even from officers — I am test-firing those firearms, determining which firearms fired which bullets, which firearms fired those cartridge cases,” said Worden.

On the day KSAT visited the lab, Worden worked on a case with more than 120 fired cartridges from four shootings. She had to compare every one of these bullets and calibers.

“I determined there’s 12 or 13 different firearms represented in shootings over a two-day period,” said Worden.

The firearms section currently has three forensic scientists. This year, Worden and her colleagues have analyzed close to 2,500 individual items of evidence. It’s over 100 items of evidence analyzed per examiner every month.

“There’s not a lot of jobs where people can say they get to shoot guns as part of their job, so it’s definitely interesting,” said Worden.


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About the Authors:

RJ Marquez is co-host of KSAT News Now and reports for Good Morning San Antonio. He's been at KSAT since 2010 and covered a variety of stories and events across the San Antonio area. He also covers the Spurs for on-air and digital platforms, including his Spurs newsletter. RJ has reported stories for KSAT Explains.

Before starting at KSAT in August 2011, Ken was a news photographer at KENS. Before that he was a news photographer at KVDA TV in San Antonio. Ken graduated from San Antonio College with an associate's degree in Radio, TV and Film. Ken has won a Sun Coast Emmy and four Lone Star Emmys. Ken has been in the TV industry since 1994.