The DNA of the man accused of killing Jennifer Hudson's family was not found on the offending weapon.
Illinois State Police forensic scientist Pauline Gordon said she tested the gun and found an inadequate measure of DNA belonging to a man.
She also stated that it excluded main suspect William Balfour.
However, Pauline added that reasons for the DNA not being present would include if the killer wiped the weapon clean or wore gloves, a Chicago court heard.
The SUV vehicle which Jennifer's perished brother Jason owned and which her nephew, Julian King, was found dead in was also tested.
She told the court she took swabs from door handles, the rearview mirror, gear shift and other areas someone might have touched.
Her colleague Robert Berk testified that he found gunshot residue on the ceiling above the rear seat of Jason's car and on a steering wheel cover in Balfour's vehicle.
According to Robert, the residue on the steering wheel cover correlated with someone firing a gun, before driving the car.
Balfour faces three counts of first-degree murder, aggravated kidnapping and home invasion in the deaths of Jennifer's mother Darnell Hudson Donerson, Jason and Julian in October 2008.
Previous witnesses have testified that the 30-year-old accused, who is the ex-husband of Jennifer's sister Julia, threatened to kill members of the Hudson family on a number of occasions.