Neil Entwistle, who was arrested Thursday in London, will not contest extradition and wishes to return to the United States "as soon as possible," his attorney Dan Brandon said at Bow Street Magistrates Court.
District Judge Anthony Evans told Entwistle that his decision to voluntarily return would be irrevocable.
"Yes, that's right," Entwistle replied. He glanced briefly at his father, Cliff Entwistle, as he signed the form consenting to return.
"He was always inclined to consent," Judith Seddon, another lawyer representing Entwistle, told reporters outside court.
Entwistle could return to the United States within a week, reports CBS News correspondent Vicki Barker (audio).
"He wants to cooperate with the authorities in any way that he can, and he is anxious that the delay may cause his late wife's family and his own additional distress, something he wishes to avoid," Seddon said. "He believes that he will receive a fair and a proper hearing in the U.S.A. of these very serious allegations."
She refused to answer a reporter who asked whether Entwistle denied the charges.
Entwistle is accused of fatally shooting Rachel Entwistle, 27, and 9-month-old Lillian on Jan. 20.
"He's facing two counts of murder, one for his wife and daughter each. And one count of a firearm possession illegal and one count of illegal possession of ammunition," Middlesex District Attorney Martha Coakley
Coakley said forensic results indicated the .22-caliber handgun used in the killings was from a collection owned by Entwistle's father-in-law. Prosecutors believe Entwistle took the gun from his father-in-law's home, then secretly returned it after the slayings.