BRUNSWICK, Ga. -

The parents of a Brunswick baby who was shot and killed in March both tested positive for having traces of what investigators believe is gunshot residue, according to a motion filed by defense attorneys in the murder case.

Thirteen-month-old Antonio Santiago (pictured below on right) was killed when prosecutors say teens De'Marquise Elkins and Dominique Lang (pictured below on left) shot him and his mother as they were walking down the street. They're both charged with murder.

The new test results have raised new questions about evidence in the case.

It's further complicating an already complicated case. It's not necessarily odd that someone who was shot, as in the child's mother, would test positive for gunshot residue, but the toddler's father did as well, and he said he wasn't there when it happened. It brings a lot more questions as the case moves toward trial.

DOCUMENT: Motion for disclosure of crime lab files

The defense attorney for filed the motion asking the judge to force prosecutors to hand over the entire Georgia Bureau of Investigation report on the slain baby's parents -- Louis Santiago and Sherry West.

West said she was shot in the March 21 incident, and Santiago said he was shopping at Walmart when it happened and wasn't there. But GBI found traces of gunshot residue, or GSR, on both.

According to the report, "This supports the possibility that the individual discharged a firearm, was in close proximity to a firearm upon discharge or came into contact with an item whose surface bears GSR." In the report, investigators noted that the particles found "also may originate from occupational and/or industrial sources."

Neither West nor Santiago have ever been considered suspects in the shooting.

West said in a phone interview the residue found on her must have come from the struggle with the teens charged in the killing. She said she didn't know why the test would come back positive for her baby's father, but insists he wasn't there.

West and Santiago are no longer together, and Santiago (pictured, below) couldn't be reached for comment Wednesday because he's in jail, being held without bail, on charges of aggravated stalking related to family violence and violation of probation.

The defense attorneys for the teens who are charged with the crime said they had no comment besides what was in the documents they filed. The district attorney didn't return a call.

The case is set to go to trial Aug. 19 in Cobb County near Atlanta.