In his book, Derry says he told two RCMP officers about the plot to murder Sean Simmons. (CBC)

A convicted drug dealer who helped carry out a Hells Angels-ordered shooting nine years ago claims the RCMP could have prevented the murder.

Paul Joseph Derry testified against his friends after the murder of Sean Simmons in Dartmouth. He now has a new name under the witness protection program.

Derry was a crack cocaine dealer and fraud artist through much of the 1990s — and a paid police informant. He doesn't duck his guilt in the October 2000 shooting.

"I am guilty as, you know, according to the Criminal Code, and I do take responsibility for my actions in it. I tried to stop the murder before it happened. I wasn't there intentionally to have Sean killed, although it may seem that way," Derry told CBC News.

Derry helped convict Neil Smith, a member of the Hells Angels, for ordering the murder, as well as three others who helped carry it out.

He claims he tried to sell information about the killing to police before it happened. In his book, Treacherous: How the RCMP Allowed a Hells Angel to Kill, he says the RCMP has to accept some responsibility for the shooting.

"I told them that I would be driving the car, that Neil Smith had ordered the murder, that Wayne James, who was my partner at the time, had taken the contract from Neil to do the killing," Derry said.

"So they knew for sure who the players that were going to commit the murder and they knew that we were all looking for this person."

Derry said he told two RCMP officers about the plan during a secret meeting in Bedford just days before the murder. He did not give them the name of the victim.

Simmons, 31, died Oct. 3, 2000, after he was shot in the head while in the lobby of an apartment building in Dartmouth. Derry drove the getaway car and hid the gun. In exchange for his testimony, he was never charged.

Smith, James and two others were later convicted of first-degree murder.

The RCMP admits its officers met with Derry before the murder, but says his information was vague and they did not believe him. The officers were cleared of any wrongdoing following a review.

"We did an internal investigation, and that was completed in 2001. It certainly showed that there was no wrongdoing on behalf of the RCMP," said Sgt. Mark Gallagher, spokesman for Nova Scotia RCMP.

Gallagher said he can't comment specifically on Derry because of the Privacy Act.

Derry said he hopes his book leads the RCMP to change some of its policies. Officers need better training in dealing with police informants who are also career criminals, he said.

Earlier this year, the Supreme Court of Canada turned down an appeal by Smith and James, who argued the jury should have been told that Derry had a reason to lie.

The Supreme Court found the trial judge had instructed the jury appropriately and had outlined Derry's criminal history and ties to police.