DNA on shell casings led to officer's killer
The ATF lab in Maryland extracted genetic material from evidence collected at the 2023 shooting of CPD Officer Aréanah Preston.
By Marco Alvarez ·
Dozens of shell casings recovered from a crime scene in May 2023 provided the key to identifying the shooter of Chicago Police Officer Aréanah Preston.
Joseph Brooks pleaded guilty to first degree murder in April 2026. His conviction relied on DNA profiles extracted from the casings found at the scene where Preston was shot and killed.
Chicago Police Chief of Detectives Kevin Bruno said the collaboration with the Bureau of Alcohol, Tobacco, Firearms and Explosives allowed investigators to process evidence that would have been difficult to analyze a decade ago. Bruno stated that DNA on the casings fired by the officer was the critical element in identifying Brooks.
Several of the casings were transported to the ATF Forensic Laboratory near Washington, D.C. The lab, led by Michelle Evans, specializes in analyzing trace human DNA from national cases involving shootings, arsons, and explosives.
Evans explained that refined techniques now allow scientists to identify multiple potential suspects from small amounts of biological material. The lab successfully developed multiple DNA profiles from the Preston case evidence.
The Chicago Police Department maintains an ongoing partnership with ATF through the Crime Gun Intelligence Center. This unit works to quickly process leads from shootings across the city. The high profile of the Preston case allowed investigators to move rapidly using this established relationship.
