Thomas, 27, of Chambersburg, was convicted by a Franklin County jury last month of second-degree murder, robbery and conspiracy to commit robbery. He was given life for the murder conviction and lesser sentences on the other convictions.
Thomas showed no emotion when the sentences were read by Franklin County Judge John Walker.
Shaw was shot twice in the head at close range on Jan. 31, 1993, while he was sitting in the front seat of a rented Oldsmobile sedan.
Thomas could have received a 10-to 20-year sentence had he let stand his 1994 guilty plea of no contest to third-degree murder. Instead, Thomas, against the advice of his attorney and the judge, withdrew his plea last February.
At the time, Assistant District Attorney David W. Rahauser said he agreed to the plea in return for Thomas' testimony against Harold Winston Noel, 23, of Chambersburg.
When Thomas withdrew his plea, Judge Walker reinstated the original charges. They included first-degree murder, conspiracy to commit murder, robbery and conspiracy to commit robbery and theft.
Thomas decided to withdraw his plea after Walker refused to give him a four-year sentence. Thomas' decision exposed him to the death penalty until prosecutors decided to seek life without parole instead.
In October of 1995, Noel entered a no contest plea to third-degree murder and was given the maximum 10-to 20-year sentence, court records said.
Shaw's body was found in the car on Warm Spring Road by a passerby.
Thomas and Noel each said they were present during the killing. They accused each other of being the triggerman. Authorities said they do not know which one actually shot Shaw.
The meeting between Shaw, Noel and Thomas involved a drug deal, authorities said.