BARNSTABLE, Mass. — During a seven-hour police interrogation, a trash collector arrested for the rape and murder of a Cape Cod fashion writer gradually moved from denying knowing the victim to offering raunchy descriptions of consensual sex with her to admitting involvement in her fatal stabbing, according to a state police detective who testified Tuesday.

The investigator, Trooper Christopher Mason, told jurors at the trial of Christopher McCowen that the turning point in the interview came when he handed the suspect a state crime laboratory report matching his DNA to semen and saliva found on the victim's body.

Previously, McCowen, 33, insisted he had never talked to Christa Worthington, a customer on his weekly route, nor visited the small cottage she shared with her toddler daughter, but after studying the report for a full minute, he looked up and said, "It could have been me," the trooper recalled.

He testified that McCowen initially claimed he had suffered an alcoholic blackout Jan. 4, 2002, the night authorities believe Worthington was murdered, and could not recall anything after visiting a bar.

"I don't remember having sex with this lady," Mason quoted McCowen as saying. The trooper said that he pushed McCowen to remember, telling him that the DNA left no doubt he was at the victim's home.

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Mason said McCowen bowed his head for a moment and then said, "Fine. I had sex with her."

The incriminating statement that followed is a complicated piece of evidence in the trial. Neither the prosecution nor the defense believes what he told the trooper is the truth.

The prosecution contends McCowen acted alone to sexually assault and kill Worthington, who did not know him, and when caught, tried to minimize his blame by saying the sex was consensual and that a friend wielded the knife.

McCowen's defense claims that he and Worthington agreed to sex and she was killed later by an unknown assailant. His lawyer has said police coerced McCowen, who he claims has an IQ of 76, into making a false statement. His lawyers have hired the country's foremost expert in coerced confessions to testify on his behalf.

Questioning the trooper Tuesday, Assistant District Attorney Robert Welsh III emphasized the voluntariness of the interview, noting that McCowen was read his Miranda rights and declined an attorney, medical attention and a phone call. Mason said investigators provided McCowen with food, drinks and water, and never yelled or threatened him.

Mason asked if he could audiotape the interview, but McCowen declined.

Over the course of hours, Mason testified, McCowen described in fits and starts how he and a friend, Jeremy Frazier, had driven from a bar to Worthington's isolated home in the cape town of Truro.

"I know this bitch in Truro who will give up some ass," Mason quoted McCowen as telling his friend.

The trooper said that despite this statement, McCowen said he had never talked to Worthington or visited her home before that night. He said the 46-year-old was "startled" when two younger, intoxicated men arrived at her doorstep, but he quickly talked her into sex.

"You can say some clever sh-- when you are drunk," McCowen said, according to the trooper. He said the suspect told him he routinely persuaded women on his trash route to sleep with him and that his standard line was, "I won't say nothing if you don't say nothing."

McCowen went on to describe a quick encounter on the floor of Worthington's living room, the trooper said. He testified that Worthington was initially "cool with it" but then began to suspect Frazier, who had wandered into her home office, was stealing from her.

"She followed them outside and was screaming at them," Mason said.

The trooper said McCowen told him that Frazier punched Worthington, who ran into the house. He said Frazier followed, came out 10 minutes later and said, "I beat her ass."

Mason was in the middle of recounting the interview when court recessed for the evening. When he resumes the stand Wednesday, he is expected to describe how McCowen ultimately said he had helped Frazier punch and kick McCowen and watched as his friend stabbed her.

McCowen, who seemed dazed or distracted during the testimony of other witnesses, seemed to be paying careful attention to Mason's account. He stared intently toward the witness stand while the trooper discussed their conversation.

Jurors have heard nothing of his extensive criminal record. McCowen served prison time in Florida on theft charges. During his seven years on the cape, five different women sought restraining orders against him.

The prosecution is prohibited from mentioning his record, but Mason said McCowen told him that "women were always getting him in trouble."

Before he admitted going to Worthington's home, he told the trooper that the 110-pound writer "wasn't his type."

He said he preferred "big girls with meat on their bones," Mason said.

The trooper said that, when McCowen was still denying involvement in the murder, he said, "his quote unquote forte was sex, not kicking in doors."

In addition to Mason's testimony, jurors also viewed a surveillance videotape of Worthington and her daughter, Ava, at a grocery store two days before her body was discovered. The panel has seen numerous photos and a videotape of her in death, but the choppy images of her pushing Ava in a cart down the supermarket aisles was a rare glimpse of her in life.

In the minute-long video, Worthington, dressed in a red coat, and Ava, in a bright blue outfit, are captured strolling through the produce section and in the cash register line. The grocery store trip was the last time Worthington was seen alive.

Also Tuesday, the judge, Justice Gary Nickerson of the Barnstable Superior Court, excused a juror who fell ill during testimony. The man appeared to faint in the jury box as a forensic analyst testified. He was taken to a local hospital by ambulance for evaluation.

McCowen faces a mandatory sentence of life in prison without the possibility of parole if convicted.

Testimony continues Wednesday morning.