MANCHESTER — Prosecutors on Wednesday dropped multiple rape charges against a 74-year-old Florida man who is a suspect in a 1984 cold-case murder.

Richard Brunt of Lakeland, Fla., faced five charges of aggravated felonious sexual assault stemming from a Manchester man’s claims that Brunt had surprised him and violated him in 2000, using a shovel at one point in the attack.

The man came forward with the allegations in 2017, after searching Brunt’s name on the internet and discovering he was a suspect in the cold-case murder.

“As we prepared (for the trial), we ran into some proof issues we couldn’t overcome,” said Brad Bolton, the assistant Hillsborough County attorney prosecuting the case. He noted the allegations are almost 20 years old.

“It’s hard to line people up after all that time,” he said.

Brunt’s attorney, Mark Sisti, said his private investigator had tracked down a minister in Longmont, Colo., who told Sisti the accuser had never informed him of the attack, which contradicted statements the accuser had made.

The minister had no reason to protect Brunt, Sisti said.

“They (the prosecutors) did the right thing. Quite frankly, they did the responsible thing,” Sisti said.

Last summer, Hillsborough County authorities had police in Florida arrest Brunt on the sexual assault charges. In the fall, he appeared in Hillsborough County Superior Court, with the accuser in the courtroom for at least one hearing.

Brunt was responsible for one death — the 1975 strangulation of his roommate, who was found naked and with “1975” written on his body in lipstick. Brunt pleaded guilty to manslaughter and spent about two years in a Florida prison.

Police have said he is the suspect in the 1984 disappearance of Massachusetts school teacher Christopher Bird, who was last seen with Brunt at the D&Q Stables in Windham. His body was never found.

New Hampshire law enforcement officials believe they have evidence Brunt killed Bird, according to previous newspaper accounts.

“He had nothing to do with that, zero,” Sisti said.

In October, a judge had set Brunt’s bail at $25,000.

But Sisti said the Valley Street jail ran into problems getting a GPS monitoring device to work in Florida. Brunt decided against being released and having to travel to New Hampshire for hearings, so he opted to remain in jail and push for a speedy trial.