Prosecutors moved Friday to conceal the names of three witnesses in last year's triple homicide near Forestville, saying their lives could be in danger if they became known to the public.

Court papers describe the witnesses as providing "relevant evidence," specifically against defendant Mark Cappello, 47 of Central City, Colo., who is accused of being the gunman in the execution-style slayings believed to have happened during a pot deal gone bad.

Deputy District Attorney Traci Carrillo is seeking an one-on-one meeting with Judge Robert LaForge in which she would explain the risks of revealing the names along with other pre-trial evidence. Her papers suggest prosecutors might ask that the witnesses be allowed to testify under pseudonyms at the July 7 trial.

"This matter involves multi-state victims and witnesses with various backgrounds and involvement in criminal activity," Carrillo said in her papers. "Three different confidential informants have provided information that they believe, if released too soon before trial, could jeopardize their safety."

Cappello, who was arrested nine days after the Feb. 5, 2013 killings, faces a possible death sentence if convicted of the murders of Todd Klarkowski, 43, of Boulder, Colo.; Richard Lewin, 46 of Huntington, N.Y.; and Raleigh Butler, 24, formerly of Sebastopol.

Two co-defendants, Odin Dwyer, 39, of Denver; and Dwyer's father, Francis Dwyer, 66, of Truth or Consequences, New Mexico, also are charged but do not face execution.

Defense lawyers would likely object to concealing the identities of the three mystery witnesses. Cappello's attorney, Michael Meehan, said the omission, coupled with incomplete forensic evidence from the Department of Justice crime lab, makes it hard to mount a defense.

"With charges as serious as my client is facing, it's hard to justify not revealing information," Meehan said.

Francis Dwyer's lawyer, Walter Rubenstein, who contends his client wasn't at the scene, said he doesn't want to be surprised by anything.

"Who are these people?" Rubenstein said. "What do they know? They could be part of an enterprise that goes all the way back to New York."

Prosecution papers say Lewin and Klarkowski first met in New York in January 2013. They hatched a plan to come to California to buy 100 pounds of marijuana through Lewin's contact, Raleigh Butler. The estimated cost was about $230,000.

Klarkowski knew Cappello and contacted him about driving the marijuana back to the East Coast, where it could be sold at a profit. Cappello hired the Dwyers to assist him.

The day of the slaying, Cappello and Odin Dwyer drove to a house off Ross Station Road to pick up the marijuana. While the victims placed it in packages, Cappello is alleged to have pulled out a gun and shot them each once in the head, according to a statement Odin Dwyer later made to police.

The two then fled with the marijuana, picking up Francis Dwyer at a Santa Rosa Avenue hotel, and drove home. Prosecution documents say Cappello read online news accounts of the slaying on his girlfriend's phone. After seeing crime scene photos that appeared to show tire tracks, he bought new tires for his Ford Bronco. A short time later, he told his girlfriend he was going on an out-of-state fishing trip and left Colorado.

He was arrested Feb. 14, 2013 as he was driving through Mobile, Ala.