Jurors began hearing testimony Monday to help them decide whether an Islamic extremist who killed eight people on a New York City bike path should get a death sentence, an extraordinarily rare penalty in a state that hasn't had an execution in 60 years.

Sayfullo Saipov, 35, was convicted last month in the 2017 attack, in which he intentionally drove a truck at high speed down a path along the Hudson River, running over bicyclists on a sunny morning hours before the city's Halloween celebrations.

The same jury that found Saipov guilty returned to work after a two-week break to hear from additional witnesses in the trial's penalty phase. Anything less than a unanimous vote for death will mean Saipov will spend the rest of his life in prison.

Assistant U.S. Attorney Amanda Houle said Saipov remains proud, defiant and unrepentant for the lives he ruined and that he remains dangerous, even behind bars. She said he once smashed his prison cell door while screaming about slitting the throats of guards.

She told jurors that Saipov smiled when he described his attack to investigators hours afterward because his massacre “made him happy.”

“He had no remorse then,” Houle said. “And the evidence will show he has continued to have no remorse.”

Attorney David Stern told jurors to let Saipov spend the rest of his life in a prison cell size of a parking space in the nation's most secure prison in Florence, Colorado.

“Sayfullo Saipov did a terrible, terrible thing, and whatever you decide, he’ll pay a terrible price,” Stern said, referencing an attack that killed five friends from Argentina, a woman from Belgium and two Americans.

He said Saipov's family members will describe the kind person Saipov was before he fell under the spell of propaganda from the Islamic State group.

Stern told jurors to “not be like him" and think death is the solution to the pain they witness.

New York does not have capital punishment and hasn’t executed anyone since 1963, but Saipov’s trial is in federal court, where a death sentence is still an option, though one rarely sought with success. The last time a person was executed for a federal crime in New York was in 1954.

President Joe Biden put a moratorium on federal executions after taking office and his Justice Department has not, until now, initiated any new death penalty proceedings.

Saipov's lawyers have argued it is unconstitutional for prosecutors to seek his execution when the government has stopped seeking death in so many other cases, including some with defendants who killed more people.

“There is no rhyme, reason, or predictability as to why the government chooses to seek death in some murder cases but not in others,” they wrote in one recent court filing.

They noted that then-President Donald Trump quickly urged a death sentence, tweeting a day after the attack that Saipov “SHOULD GET DEATH PENALTY!” The lawyers said it was Trump’s way of furthering “his anti-immigrant agenda.”

“There is a legitimate concern that the death penalty sometimes (and impermissibly) turns on the defendant’s race, ethnicity, national origin, and religious beliefs,” they wrote.

Judge Vernon S. Broderick rejected the argument Monday before opening statements in the penalty phase began.

Houle told jurors that more victims will describe their pain during the penalty phase. In the first phase of his trial, jurors heard from survivors who described the horror and sorrow at losing loved ones and the pain they continue to suffer from injuries.

Stern acknowledged that Saipov has been unrepentant since he was shot after emerging from his truck and waving pellet and paintball guns at a police officer. Later, in a hospital bed, the Uzbekistan citizen smiled as he requested that a flag of the Islamic State group that inspired his rampage be put on his room's wall, prosecutors said.

Prosecutors plan to introduce evidence intended to show jurors that, if kept alive, Saipov may still be able to communicate with sympathizers.

Saipov’s lawyers said before trial that he would be willing to plead guilty and consent to life in prison if death was not sought.

Any death sentence rendered by the jury would likely by subject to years of appeals.

New York's last federal death penalty case involved a man who murdered two police officers in 2003. Federal juries in Brooklyn twice imposed a death sentence, first in 2007 and again in 2013, but each time that sentence was ultimately overturned on appeal.