When firearms expert Stephanie Stewart tries putting "trigger pull weight" into layman's terms, she starts with a simple frame of reference: it takes 6 pounds of force to open a can of soda.
In testing the .22 caliber rifle used in the fatal shooting of 39-year-old Kelly Ann Rowles, Stewart found a trigger pull weight of 7 1/4 pounds. The weight, Stewart testified Friday, was "significantly more" than the hair-trigger range of 2 pounds.
Stewart's testimony during the second day of the juvenile manslaughter case against Rowles' teenage son, Jonathan, brought into question the nature of the shooting, which the now-15-year-old has said was accidental. In an August 2010 interview with police after the shooting, Rowles, 13 at the time, said he had the rifle aimed at his mother with his finger on the trigger, then accidentally fired. He never gave a clear reason for what caused the trigger pull, though at one point he alluded to dog barks that spooked him.
Stewart, a Florida Department of Law Enforcement expert, said the rifle used in the shooting fired properly during three test shots. The safety functioned correctly, and the bullets fired without issue on all three shots. The only malfunction came on the third shot, when the cartridge failed to properly eject. The failure, however, wouldn't contribute to an improper shot, Stewart said.
"That didn't preclude it from firing," Stewart said.
Questions to Stewart from Rowles' lawyers focused on a tubular magazine that was out of investigators' hands for 45 days, an apparent oversight during the process of collecting evidence from the shooting scene. His lawyers previously sought to exclude evidence related to the rifle, arguing the possibility of tampering. Their motion was denied Thursday.
Stewart testified the tubular magazine didn't affect testing for the trigger pull or proper functioning of the rifle's safety mechanism. Rowles' assistant public defender, Justin Barger, declined to comment after the hearing about the trigger pull testimony.
Before Stewart took the stand, Collier County Sheriff's Office crime scene investigator Alicia Craig testified, laying out the shooting scene. Photographs taken by Craig showed Kelly Rowles was sitting on a chair up against a wall in a television room when she was shot. Physical evidence suggested Kelly Rowles was hit in the upper left temple with a clean shot from behind. The shot was fired from an adjacent living room through a narrow entryway between two walls. She likely didn't see her son in the moments before the shooting, evidence showed.
"Based on the fact there are no holes in the walls or the chair itself, there would have to be a certain limited amount of sight," Craig said.
In the hours after the shooting, Rowles told investigators he had been imitating U.S. Marines by twirling the rifle and aiming it at various objects. Rowles said he then turned the rifle toward his mother, accidentally pulling the trigger.
The trial continues Monday, with the medical examiner and lead detective taking the stand.
If convicted, Rowles faces various sentencing outcomes, though none involve prison. He would be out of the juvenile justice system no later than age 21.