A career criminal serving a life sentence for killing a Long Island cop during a 2012 traffic stop was found dead in his upstate prison cell, according to authorities.

Darrell Fuller, 40, who was convicted of murder in 2014 for gunning down Nassau County Police Officer Arthur Lopez, was pronounced dead after he was found unresponsive in his cell at the maximum-security Elmira Correctional Facility on Dec. 9, state corrections officials said Monday.

A state police spokesperson told The Post Fuller’s death is under investigation, but is not believed to be suspicious. A law enforcement source said Fuller had been plagued by health problems.

Fuller was sentenced to life without chance of parole for the brutal Oct. 23, 2012, slaying of the 29-year-old cop.

“You, despicable you, are not going to see the light of day henceforth or forever,” Supreme Court Justice Jerald Carter told Fuller at his sentencing.

“Is there anything redeemable about you? The answer is no,” the judge said. “You have taken it upon yourself to be God and executioner on the street.”