The attorney for the Manorville carpenter on trial for killing two women more than 20 years ago suggested to a jury Wednesday that two police officers may have been the real killers.

Perhaps that explains why Suffolk police over the years have destroyed all the physical evidence collected from the crime scenes and the officers, William Keahon said in his opening statement.

“You think this is coincidence?” Keahon said. “How many times do they tell you, ‘We screwed up’ ?”

John Bittrolff, 50, was charged in 2014 with two counts of second-degree murder in the killings of Rita Tangredi, 31, of East Patchogue on Nov. 2, 1993, and Colleen McNamee, 20, of Holbrook on Jan. 30, 1994, based on what prosecutors say is a DNA link between him and semen found on Tangredi and McNamee, who both worked as prostitutes.

The trial is before state Supreme Court Justice Richard Ambro in Riverhead.

Both women were severely beaten and strangled, posed identically and covered with wood chips, Assistant District Attorney Robert Biancavilla said.

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He conceded that there “were speed bumps and there were hiccups along the way” in the investigation, referring to the destruction of evidence. He said DNA ruled out the Suffolk County police officers — former Officer Teddy Hart and then-Sgt. Michael Murphy, since promoted to lieutenant — as the killers.

“This case is about science, ladies and gentlemen,” Biancavilla said. “The killer left his calling card on these girls. The killer left his signature style on these girls. But he also left his genetic fingerprint.”

Biancavilla also asked why Bittrolff would lie after his arrest about being the source of the DNA.

Keahon had an answer: “I don’t know a guy that would say, ‘Yeah,’ in a police station when it’s a crime to be with a prostitute. And you’re married. And you have two sons.”

The defense attorney dismissed the importance of the DNA evidence.

“I’m going to ask you, why does he have to be the killer?” Keahon said. “Sexual relations don’t equal a killer.”

Many others were more likely killers, he said. Besides Murphy and Hart, Keahon said both women had been threatened with death by others.

But Keahon said the destruction of evidence collected at the crime scenes — including the wood chips — and evidence he said was collected from Hart’s and Murphy’s cars was most damning.

“I can’t see it,” he said. “I can’t have it analyzed if I want to. They destroyed it.”

The Hauppauge attorney said he hoped jurors find out what Murphy did to become a suspect in 1998. In Hart’s case, Keahon said that was clear.

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“This fellow, he made telephone calls to women and threatens to rape them,” Keahon said. “He threatened to mutilate them and watch the blood ooze out of them.”

Still, one of Tangredi’s sons, Anthony Tangredi, now 34, told reporters he was sure Bittrolff was the killer.

“People can hide their true selves really well,” he said.

Keahon asked the first witness, Det. James Johnson, if he saw any wood chips on or near Tangredi’s body when he examined the crime scene.

“I don’t recall seeing any,” Johnson said. “It was primarily plant material.”