An Islip woman Tuesday tearfully identified the clothing worn by her 18-year-old son when he left his house the night he was choked and buried alive by a friend and former classmate who now stands charged with murder.

Aimee Underhill-Catanzaro, 42, dabbed at her eyes as she looked at the picture of her son, Kyle Underhill, and noted the object sticking out of his shirt pocket was the flat item he used to scrape crumbs from the tables at the steakhouse where he worked.

"He thought it was the coolest thing when he got it," she said during the first full day of testimony at the murder trial of Thomas Liming, now 23, of Islip, in state Supreme Court in Riverhead.

In opening statements Monday, the defense did not contest that Liming was responsible for Underhill's death.

Prosecutors contend Liming choked and severely beat Underhill on the night of Nov. 16, 2011, and buried him in the dense woods off Brook Street in Islip.

Defense attorney Joseph Corozzo of Manhattan has not indicated what type of defense he will mount, but did not disagree when Judge Mark Cohen said Tuesday outside the presence of the jury that he was anticipating a psychiatric defense.

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Corozzo spent much of his time on cross-examination trying to get Underhill-Catanzaro to say her son by her prior marriage had trouble of some sort, and to concede her son might have been angry that Liming did not come to his high school graduation party in July 2011.

She insisted her son was "upset," not angry. "He was an 18-year-old and his friend didn't show up. He was upset," she said.

Underhill-Catanzaro trembled and choked up at times during her testimony, and the judge called a short recess in the morning session to allow her to collect herself.

She conceded during testimony in the afternoon that some of her recollections -- such as how often she met Liming -- were at variance with her testimony before a grand jury in 2013.

"It's very stressful," she said. "I don't remember what I said. I don't have the grand jury minutes in front of me."

Prosecutors said the Liming family stonewalled the investigation, and Det. Gary Travers, who was assigned to the missing persons section in 2011, said he and his partner went to the Liming home at 3:30 a.m. the night after the killing and before the body was found.

There were cars in the driveway and on the street in front, but no one answered his repeated knocks on the door, he said.

The trial resumes Wednesday.