BOSTON (AP) – A federal jury began deliberating Friday on whether Gary Sampson should be executed for carjacking and murdering a 19-year-old college student and a 69-year-old retiree during a weeklong crime spree in 2001.

Sampson, 44, a drifter who grew up in Abington, faces either life in prison or death for the killings, which prosecutors argued were committed in an especially heinous, cruel and depraved way.

The jury of nine women and three men began considering Sampson’s fate shortly after 2 p.m. Friday after receiving instructions on the federal death penalty from U.S. District Judge Mark Wolf.

Jurors spent just under two hours deliberating before leaving for the weekend without reaching a verdict. Deliberations were scheduled to resume Monday.

Wolf said the jury must weigh aggravating factors presented by prosecutors against the mitigating factors presented by Sampson’s lawyers in deciding his punishment.

Sampson stabbed Philip McCloskey, an elderly grandfather from Taunton, 24 times, and Jonathan Rizzo, a college student from Kingston, 15 times, several days apart in July 2001 after each man picked him up hitchhiking.

Prosecutors told the jury that Sampson’s admitted murder of a third man during the same week should be considered in their decision. Sampson confessed to strangling Robert “Eli” Whitney in Meredith, N.H., several days after he killed Rizzo.

As a mitigating factor, Sampson’s lawyers cited a call Sampson made to the Boston FBI the day before he began his killing spree. Sampson said he tried to give himself up, but the call was accidentally disconnected by an FBI clerk.

Sampson’s lawyers also argued that he is mentally ill, suffers from bipolar disorder and was withdrawing from drugs at the time of the killings.

Massachusetts does not have a state death penalty statute. Prosecutors charged Sampson under a federal statute that allows the death penalty when a murder is committed during a carjacking.

Wolf told the jurors they have a “profound decision” to make.

“In this sense, each of you is responsible for deciding whether Mr. Sampson will live or die,” he said.

Jurors must be unanimous in determining whether prosecutors have proven any aggravating factors, which Wolf described as circumstances that make a killing especially egregious.

Prosecutors have argued that Sampson inflicted physical abuse on his victims over and above what was necessary to kill them.

If the jurors cannot reach a unanimous decision on the death penalty, Sampson will automatically get life in prison.

The jury does not have to be unanimous when deciding on whether the defense has proven certain mitigating factors – circumstances of the crime or Sampson’s background that make life in prison a more appropriate sentence.

However, Wolf told jurors they should not simply count up the number of aggravating and mitigating factors and vote according to which side – the prosecution or defense – has the highest number. He said each juror must decide how much weight or importance to give each factor in making their ultimate decision on whether to vote for the death penalty or life in prison.

“This is not a matter of arithmetic,” he said.

AP-ES-12-19-03 1657EST