BANGOR, Maine — There’s no doubt that Joseph Dumas, 49, shot his best friend fives times after snorting a lot of cocaine.

The question the jury will have to decide is whether it was murder or manslaughter.

The murder trial of the Prentiss man charged with killing 70-year-old Mario “Sonny” Litterio of Prentiss got under way Monday with opening statements in Penobscot County Superior Court. Dumas has admitted shooting Litterio on Nov. 8, 2007, near a camp on Tar Ridge Road in Prentiss where Dumas was working.

Assistant Attorney General Donald Macomber told the jury of seven men and seven women, which includes two alternates, that Dumas intentionally or knowingly shot Litterio twice in the shoulder and twice in the head with Litterio’s own gun. The defendant then literally blew the victim’s head off when he shot him a final time with .50-caliber muzzleloading black powder rifle, Macomber said.

Defense attorney Richard Hartley of Bangor told the jury that Dumas was bingeing on cocaine the day he killed his friend and did not intentionally or knowingly murder Litterio. Hartley said the evidence would show that Dumas is guilty of manslaughter, not murder, due to his intoxicated state at the time he pulled the triggers.

If convicted of murder, Dumas faces a minimum sentence of 25 years and a maximum sentence of life in prison without a chance of probation. If he were convicted of manslaughter, he would face a maximum sentence of 30 years in prison and would be eligible for probation.

For much of Monday, Jason Litterio, 20, of North Scituate, R.I., sat directly behind the man accused of murdering his father 18 months ago. The young man took the stand briefly Monday morning to explain how on Nov. 9, 2007, he drove to his father’s home from Fairfield, where he was a student at Kennebec Valley Community College, when he couldn’t get in touch with him.

“I showed up and the [Maine State Police] were there,” Litterio said during an afternoon break. “I let them inside the house and showed them around.”

He did not learn until the next day that Joseph Dumas had killed his father.

“His family was my second family,” Litterio said.

State police Detective Darryl Peary testified Monday afternoon about his interviews with Dumas and the discovery of Litterio’s body. A 90-minute taped interview from Nov. 9, 2007 — in which an emotional Dumas recalled shooting his friend — was played for the jury.

Dumas, his hair closely cropped and his face cleanly shaven except for a moustache, sat at the defense table. Dressed in a blue dress shirt, gray slacks and striped tie, Dumas wept as he listened to himself describe emptying a revolver into his best friend.

He told police that while working on renovations to the camp, he snorted cocaine. At one point, Dumas said that he was outside and saw a deer in the woods behind the cabin. He shot at it with his black powder rifle and thought that by the way it acted, he had wounded it. Dumas told Peary that he drove the short distance to the victim’s home, which is located on the same road, and asked Litterio to help him look for the deer.

After Litterio got a revolver from a kitchen drawer, the men went back to the camp in Litterio’s pickup, Dumas said on the tape. Dumas told police that he and his friend went down a tote road toward where he said he had seen the deer.

Litterio said he had to urinate and handed his gun to Dumas to hold, according to Macomber. As the victim walked toward a tree, Dumas shot him with the .38-caliber revolver — twice in the shoulder and twice in the head, Dumas said on the tape. He said he again shot Litterio with the black powder rifle, which he at some point had reloaded.

Peary showed the jury photos of the victim’s body as police found it on Nov. 10, 2007, using a map drawn by Dumas. Litterio was lying face down in a pile of leaves, his hands underneath him.

The detective also displayed a photo taken when Litterio’s body had been turned over. It showed that his zipper was down.

Superior Court Justice Michaela Murphy is presiding over the trial, which is expected to go to the jury on Thursday.