By Ann Givens, The Trace

Police found 19 spent shell casings scattered in the San Diego street where Gregory Benton was murdered on April 12, 2014. Benton and his cousin had gone to buy cigarettes, a witness later said. As they returned to a family party, two men pulled up in a car behind them. They got out, and at least one of them opened fire.

Witnesses didn’t get a good look at the men or the car, so when police sat down to review their leads, the shell casings were the best evidence they had. They sent the casings to the San Diego Police Crime Lab, which just happened to be trying out a new DNA testing technique.

Previously, to remove DNA from casings, the lab would moisten a cotton swab and rub it over the metal. But their success rate was less than 1%. This was proving to be a problem for many cities across the country struggling to solve shootings and homicides. Police often find that shell casings they collect from a crime scene are their most valuable evidence. Ballistic testing can offer clues about what kind of gun was used and, sometimes, whether that same gun was used in another crime. But the casings seldom yielded fruitful DNA results, and the San Diego Police Department, like many others, had stopped testing them.   

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Testing the casings for DNA would likely delay getting a NIBIN lead. In San Diego, where police now ask for DNA testing on the majority of casings collected in homicides, it takes the lab about eight days from when police pick up a casing off the street to the time they get it into NIBIN. That’s about two days longer than it would otherwise take them.

“The DNA portion does slow down the NIBIN entries,” said San Diego lab director Jennifer Shen in an email. “Although we certainly think it is worth it, as do our customers.”