The first thing a forensic scientist noticed 23 years ago in some brush just south of the Long Island Expressway in Shirley was a woman’s blue winter jacket.

Next, on the evening of Jan. 30, 1994, came a sock, Philip Antoci testified Tuesday in Riverhead at the trial of John Bittrolff, 50, a Manorville carpenter. Then another sock and a sneaker. Then one pair of blue pants hanging in a bush and another pair nearby. And then, finally, Antoci — formerly of the Suffolk County Crime Laboratory — saw the naked body of Colleen McNamee, 20, the Holbrook woman whose killing had brought him there.

Red marks covered one of her legs and extraordinary violence had been done to her head. Her body was posed, legs apart and her right arm above her head. Clutched in her left hand, near her face, was her sweatshirt. During questioning by Assistant District Attorney Jen Milito, Antoci said McNamee’s body went to the medical examiner’s office with the shirt still in her hand.

Bittrolff is charged with second-degree murder in the deaths of McNamee and of Rita Tangredi, 31, of East Patchogue on Nov. 2, 1993.

Crime scene photos and videos have shown some similarities between the two killings. Both had severe head trauma. Both bodies were naked and posed with legs apart, although Tangredi had both hands above her head. Both were left with a single shoe near their bodies.

Tangredi’s body was covered with leaves and vegetation, while McNamee’s was not. The Tangredi crime scene was marked by blood on leaves and trees, but no blood stains were visible on the snow near and beneath McNameee’s body.

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Also not visible in either crime scene have been the wood chips that Assistant District Attorney Robert Biancavilla has said were the “calling card” that Bittrolff left on his victims’ bodies.

“Did you see any wood chips on her body?” defense attorney William Keahon of Hauppauge asked during cross-examination.

“No, I did not,” Antoci said. Earlier in the trial, a detective who also didn’t notice wood chips said the crime lab would have noticed and collected any wood chips.

Antoci said there were none in the area or on any of the clothes at the scene.

The two cases remained dormant for years, until Aug. 11, 2013, when Joseph Galdi, director of biological sciences at the crime lab, said the state informed him it had a partial match to DNA found in semen left on Tangredi’s body.

“We waited a long time,” Galdi said. “We waited 13 years.”

That partial match was to Bittrolff’s brother, Timothy. Police later got John Bittrolff’s DNA, which was matched to DNA on both bodies.

Keahon has said his client’s DNA on both bodies is not evidence that he killed them.