WOBURN, Mass. -- The gun prosecutors said Neil Entwistle used to kill his wife and daughter will be the focus of his double-murder trial on Monday.

Entwistle, 29, is accused of shooting his wife Rachel, 27, and 9-month-old daughter, Lillian Rose, on Jan. 20, 2006, in the family’s rented home in Hopkinton.

Special Section: Entwistle Trial

The weapon is a key part of the prosecution’s case. Assistant Middlesex County District Attorney Michael Fabbri said Friday that Neil’s and Rachel’s DNA was found on the .22-caliber Colt revolver owned by Rachel’s stepfather. Neil Entwistle is accused of stealing the gun from Joseph Matterazzo's Carver, Mass., home and returning it after the slayings.

"The DNA of Rachel Entwistle -- who had no interest in firearms, who had never touched those firearms -- was on that .22-caliber Colt," Fabbri said.

Neil Entwistle’s in-law Lloyd Cooke, of Pembroke, testified to Neil Entwistle’s experience with guns on Friday, saying he knew how to handle a gun and was an accurate shooter.

Cooke will be back on the stand in Middlesex District Court in Woburn on Monday.

Hopkinton police found the bodies of the young mother and baby under bedding and pillows in the home’s master bedroom on Jan. 22, 2006, after her family filed missing persons reports.

Neil Entwistle later said he found the bodies when he got home from running errands on Jan. 20, 2006, and bought a one-way ticket to his parents’ home in England without calling police or Rachel Entwistle's family.

His defense told jurors he was a loving and devoted husband and father whose reactions after the slayings were consistent with a grieving father.

Neil Entwistle has pleaded not guilty to two counts of murder, illegal possession of a firearm and illegal possession of ammunition.

The trial could run until the first week in July.