ATF Lab Helps Link Suspect to Officer's Killing
Forensic analysis of shell casings led to Joseph Brooks, who has pleaded guilty to the first-degree murder of Chicago police officer Aréanah Preston.
Updated on Nov. 6, 2026 in Law Enforcement
Joseph Brooks pleaded guilty in April 2026 to first-degree murder in the killing of Chicago police officer Aréanah Preston, who was shot in May 2023. DNA on shell casings recovered from the scene, analyzed by an ATF forensic lab, was key to identifying him.
Why it matters
The case shows how Chicago police and the ATF's Crime Gun Intelligence Center worked together to move quickly after an officer was killed. For Chicago residents, it highlights the role of federal forensic resources in solving serious violent crimes.
Joseph Brooks has pleaded guilty to first-degree murder as of April 2026. The extraction does not specify a sentence or sentencing date.
The players
Joseph Brooks
Brooks is the man who pleaded guilty to first-degree murder in the killing of Chicago police officer Aréanah Preston.
Aréanah Preston
Preston was a Chicago police officer shot and killed in May 2023, whose case led to the identification of her killer.
Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF)
The ATF is the federal agency whose forensic lab in Maryland analyzed the shell casings and developed the DNA profiles used in the investigation.
The details
Dozens of shell casings were recovered from the scene, and some were flown to the ATF forensic lab in Maryland, which developed multiple DNA profiles from them. The DNA on casings fired by the killer was key to identifying Brooks.
Timeline
May 2023: Officer Aréanah Preston was shot and killed in Chicago.
April 2026: Joseph Brooks pleaded guilty to first-degree murder.
Legal Context
The case illustrates how the Chicago Police Department works with the ATF through the Crime Gun Intelligence Center to analyze firearm evidence. Shell casing DNA analysis has become a tool in tracing shooters in violent crime cases.
Chicago residents may see continued cooperation between local police and federal agencies on firearm investigations. The case reflects how forensic evidence from shell casings can be used to identify suspects in violent crimes.
The takeaway
Forensic evidence such as DNA on shell casings can be decisive in identifying suspects, and it depends on coordination between local police and federal labs.
Further reading
Explore more coverage in Law Enforcement for context on police investigations in Chicago.
Source note: This article includes information reported by ABC7 Chicago.
