Cuts in the underwear show where police took DNA samples. (CBC)

Charlottetown police believe a small pair of bikini-style underwear, containing DNA of both a male and a female, belonged to the killer of Byron Carr.

"It's an item of clothing that was left at the crime scene," said Charlottetown police Sgt. Brad MacConnell.

Carr, a former school teacher, was found strangled and stabbed in his home on Nov. 11, 1988. The file lay dormant for years, but police reopened it in October 2007. They hoped new technology might assist in the investigation, and that a better relationship between the gay community and the police might help.

Police believe Carr was killed by a gay sexual partner that he picked up.

Police displayed on Tuesday a piece of clothing found at Carr's Lapthorne Avenue home: small-waisted Zellers brand men's bikini-style briefs, sold only in Canada.

The underwear demonstrates the person was small in stature, MacConnell said. Police displayed it on a mannequin with a 29.5-inch waist, and it was a snug fit.

Police believe the killer was between 16 and 30 years old at the time.

One thing investigators are hoping for is that the female whose DNA is on the underwear, with whom police assume the killer had a close relationship, might come forward.

"If you're the female subject you may have a visual recognition of it," said MacConnell.

"However, we're trying to give people an idea of the size of the person we're looking for."

The female DNA on the underwear suggests the killer could have been bisexual, said MacConnell.

He also said forensic testing has convinced officials that Carr's death was not an accident.

"It's been widely speculated in the public in the past that this was an accident, death by misadventure," MacConnell said. "We want to make it clear that this is a murder."

Police have held several news conferences since reopening the investigation, outlining a possible connection between a car theft and the murder, and displaying a sketch of a person of interest.