WOBURN, Mass. - A police detective testified Tuesday that a laptop computer taken from the home of a British man accused of killing his wife and 9-month-old daughter was used to search online for "how to kill with a knife" four days before the slayings.

Medford police Detective Lawrence James, a computer expert, said the Google search was done on Jan. 16, 2006. Neil Entwistle has pleaded not guilty to murder charges stemming from the killing of his 27-year-old wife, Rachel, and their daughter, Lillian Rose, in their rented Hopkinton home on Jan. 20, 2006.

The 29-year-old Entwistle told police he returned home from shopping to find the victims dead in a bed in the master bedroom.

Prosecutors, however, sought to indicate that Entwistle was planning to kill his wife and child, saying that he researched methods of murder and suicide in the days before he fatally shot them.

James is expected to testify more about Entwistle's computer use Wednesday. Judge Diane Kottmyer ruled Tuesday that prosecutors will be allowed to present evidence that Entwistle trolled the Internet looking for sex in the days before the slayings.

James testified in previous court filings that Entwistle allegedly looked for local escort services using search terms that included "half-priced escorts," and that he joined a Web group called "Adult Friend Finder," where he exchanged e-mails with women saying he was looking for a "discreet" sexual relationship.

A chemist also testified Tuesday that Entwistle's DNA was found on the handle of the .22-caliber handgun used in the shootings, while his wife's DNA was found on the muzzle.

Prosecutors say Entwistle stole his father-in-law's gun from his home in Carver, used it to kill his wife and daughter at their home in Hopkinton, then returned the gun.

Entwistle's father-in-law, Joseph Matterazzo, testified earlier Neil Entwistle handled his guns when they went target practicing in the months before the killings.