BOSTON—  As a federal judge began hearing arguments Monday in a request for a new trial from a man who was sentenced to death after killing three people, the son of one of his victims said he wished the family members could be watching a different proceeding.

“We should basically be going down to watch his execution, not going through this again,” said Scott McCloskey, the son of Philip McCloskey, 69, of Taunton, who was killed by Gary Lee Sampson in July 2001.

McCloskey was joined in court by a brother and two sisters, and relatives of Jonathan Rizzo, a college student from Kingston who was also killed by Sampson.

Sampson, a drifter who was raised in Abington, argues 18 grounds for a new trial in a petition that centers on his claim that his former lawyers did not give jurors a full picture of his troubled life. If they had, Sampson’s new lawyers argue, jurors may have spared his life and sentenced him to life in prison.

Sampson pleaded guilty to carjacking McCloskey and Rizzo after each man picked him up hitchhiking. He said he forced both men to drive to secluded spots, told them he wanted to steal their cars, then stabbed them and slit their throats.

Sampson then fled to New Hampshire, broke into a house in Meredith and strangled Robert Whitney, 58. He received a life sentence in that killing.

At the sentencing trial, Sampson’s lawyers said he suffered from bipolar disorder, damage to the frontal lobe of his brain and drug and alcohol addiction and was abused as a child.

Sampson lost an appeal to 1st U.S. Circuit Court of Appeals, and the U.S. Supreme Court refused to hear the case.

On Monday, U.S. District Judge Mark Wolf heard prosecutors’ arguments that Sampson’s latest appeal should be dismissed without further hearings.

One of the arguments made by Sampson’s new lawyers is that his former lawyers did not call anyone from his family to testify on his behalf.

Prosecutors maintain that Sampson’s former lawyers tried to get Sampson’s family to testify for him, but they did not respond to repeated requests.

After hearing arguments, Wolf said he would not dismiss several claims immediately and may ask for more information or may hold a full hearing on the claims at a later date. Those include claims that Sampson’s old lawyers should have investigated more thoroughly reports that Sampson was physically abused by his father as a child.

The hearing was expected to continue today.