Anthony Kidd, 38, used the smuggled phone to call his brother, Henry Kidd, and their cousin, Darrell Scott, and to lure his girlfriend to the location of the shooting, according to investigators.
All three have been charged in the death of Kendra Degrasse, 33, of Trenton, who was found dead in the driver's seat of her Nissan Pathfinder, shot multiple times in the head.
Anthony Kidd, who is serving time for shooting at two police officers during a 2001 car chase, wanted Degrasse killed in retaliation for statements she initially gave implicating him and had sent her a letter telling her she was "a dead person walking," said Mercer County Prosecutor Joseph Bocchini.
Anthony Kidd was charged with murder and conspiracy to commit murder.
Henry Kidd, 40, was served with the criminal complaint at a state prison in Huntingdon, Pa., where he is serving time on robbery and assault charges. He was charged with conspiracy to commit murder. He would have be eligible for release in October, according to corrections officials.
Scott, 40, was arrested last week at his home in Georgia. He was charged with murder, conspiracy to commit murder and weapons charges. He was awaiting extradition to New Jersey.
The Associated Press requested to speak to all three men, but none of the suspects was made available for comment Thursday. The case had gone cold, but Trenton Police Director Irving Bradley said police had not given up.
"We might hit roadblocks, but we never quit or cease to investigate," he said.
New Jersey Corrections Department spokeswoman Deirdre Fedkenheuer said the department has trained cell phone-detection dogs, but the problem persists in New Jersey prisons and elsewhere.
She said the department is lobbying the state's congressional delegation for passage of the Safe Prisons Communications Act, legislation that would permit the use of cell phone jamming in prisons under certain circumstances.
"Until cell phones are rendered useless within jails and prisons," Fedkenheuer said, "the safety of staff and the public will be in jeopardy."
