About five years after two women were killed in similar circumstances, two top Suffolk police officials secretly focused on one of their own as a possible suspect, the director of the Suffolk County Crime Laboratory testified Monday at the trial of another man charged years later.

Robert Genna said Det. Lt. John Gierasch, commander of the Suffolk police Homicide Bureau, asked him and another forensic scientist to go to Nolan’s Auto Body on Waverly Avenue in Patchogue to examine a police car that had been in a crash on Nov. 12, 1998. Genna said Gierasch told him the car’s driver, then Sgt. Michael Murphy, was a suspect in the killings of Rita Tangredi, 31, of East Patchogue on Nov. 2, 1993, and Colleen McNamee, 20, of Holbrook on Jan. 30, 1994.

At the shop, Genna said he met with Gierasch and Lt. Peter Esposito of the Internal Affairs Bureau and then collected everything from the car — napkins, a towel, soda bottles — that might have Murphy’s DNA on them.

During questioning by Assistant District Attorney Robert Biancavilla, Genna said he also noticed and collected wood shavings next to the driver’s seat.

“They were shavings similar to what you would get sharpening a pencil,” Genna said.

He testified in Riverhead at the second-degree murder trial of John Bittrolff, 50, a Manorville carpenter who was arrested in 2014 after his DNA was linked to both victims. Murphy has since been promoted to lieutenant.

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Biancavilla has said that “wood chips” — actually microscopic particles — left on both victims’ clothing was part of Bittrolff’s “signature style.”

The wood shavings from Murphy’s car were “grossly dissimilar” to those particles, Genna said.

“Do you still have these wood shavings?” defense attorney William Keahon of Hauppauge asked during cross-examination.

“No,” Genna said.

“Where are they now?” Keahon asked.

“I don’t know,” Genna said. “You’d have to ask the police department.”

“You know they were destroyed, don’t you?” Keahon continued, and Genna agreed.

Keahon also asked Genna if the investigation of Murphy was kept confidential “because his father was chief of detectives in the police department,” but state Supreme Court Justice Richard Ambro sustained an objection to the question.

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Although Genna said the shavings were “grossly dissimilar” to the crime scene particles, Keahon pointed out what appeared to be particles visible in photos of the floor of Murphy’s car. Genna said he didn’t collect or examine those.

Genna told Keahon he couldn’t recall if Gierasch said Murphy was also a suspect in other unsolved murders and rapes.