The jury trying Briton Neil Entwistle for the murder of his wife and baby will be allowed to hear evidence that he trawled internet sex sites in the days before the killings, the judge has ruled.
US prosecutors will also be allowed to introduce evidence showing Entwistle used his laptop computer to search for local escort services and to join a website called Adult Friend Finder to look for a sexual relationship.
Meanwhile, the trial was told that DNA on the grip of a gun used to kill his wife and baby was five billion times more likely to be his than any other white male.
The 29-year-old former IT worker’s DNA also matched profiles found on the gun case for the revolver, a gun lock and a green metal ammunition can, forensic scientist Laura Bryant said.
Entwistle denies murdering his 27-year-old American wife Rachel and their nine-month-old daughter Lillian at their new home in Hopkinton, Massachusetts, on January 20, 2006.
His wife previously taught at St Augustine’s Catholic High School in Redditch and lived in Droitwich during her three years there.
The gun’s owner, Entwistle’s father-in-law Joseph Matterazzo, other members of the Matterazzo family who went sports shooting at the same club, and Rachel Entwistle were all excluded from the DNA found on the gun’s grip, the court heard.
Ms Bryant, a supervisor with the Massachusetts State Police crime laboratory, said the DNA sample taken from the grip of the .22 Colt revolver was one in 5.299 US trillion (5.299 UK billion) times more likely to be from Entwistle than any other white male.
But the DNA of Mr Matterazzo, who used the revolver at his gun club the day after the murders, was found on the trigger while Entwistle’s was not, the court heard.
Ms Bryant also told the jury at the Middlesex County Superior Court in Woburn, Massachusetts, that blood on the front muzzle area of the gun was 21.82 US quadrillion (21.82 UK thousand billion) times more likely to be from Rachel than any other white woman.
The jury has heard that a post-mortem examination found Mrs Entwistle was shot in the forehead at close range and Lillian was killed with a bullet which passed through her abdomen and lodged above her mother’s left breast as she cradled her in the four-poster bed in the master bedroom of their home.
Assistant District Attorney Michael Fabbri, prosecuting, has said Entwistle had a secret life in which he trawled the internet for escorts and looked at websites about bankruptcy, killing and suicide before shooting his family.
He faces life in prison without the possibility of parole if convicted of the double murder.