A Cook County judge ruled Thursday that key witness testimony from a firearms expert will be allowed in the trials of three men accused in the murder of Chicago police officer Areanah Preston.

Preston, 24, was shot and killed outside her Avalon Park home in May of 2023, just after finishing her shift. She was just starting her police career and only days away from earning her master's degree.

About 40 people, all of them Preston's family, friends, and fellow officers, packed the courtroom as three of the four suspects asked a judge to block a firearms expert from presenting testimony on firearms and ballistics evidence in the case.

Defendants Trevell Breeland, Jakwon Buchanan, and Jaylen Frazier were all present at the hearing. Their attorneys argued firearms evidence presented in their cases should not be allowed at trial.

That includes ballistics evidence, the kind of testimony where an expert claims a bullet or casing can be matched to a specific gun.

The trio's attorneys said the testing is subjective, and there are not enough safeguards to prevent bias.

They also pointed to recent court decisions — including one in Cook County last year — where judges said this type of firearms testimony isn't reliable enough.

Prosecutors have brought in a U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives expert to testify in this case. She told the court bullets and shell casings in this case came from specific guns.

The suspects' attorneys claimed that level of certainty can be misleading—especially to an unknowing jury.

But the judge in their case ruled firearms testimony is not new or novel, and is generally accepted and her court will continue to follow the law, and not the outlier cases presented on behalf of the defense.

Next week, the fourth suspect charged in Preston's murder, Joseph Brooks, will be in court for a status hearing. He had previously tried to get the incriminating statements he made to police thrown out, but that was denied. He was not part of the effort to bar firearms expert testimony.

All four face multiple felony charges, including first-degree murder, armed robbery, possession of a stolen vehicle, and burglary.

Police have said the four men tried to rob Preston, who was off duty but still in uniform, as she was just getting home from work in the 8100 block of South Blackstone Avenue on May 6, 2023. At least two of the suspects started shooting at Preston, who returned fire.

Investigators have said all four were also connected to multiple robberies and a car theft before killing Preston. All of them have lengthy juvenile records.

No trial dates have been set yet.