By Jonathan Allen

NEW BRUNSWICK, New Jersey (Reuters) - A former Rutgers student on trial for allegedly spying on the homosexual tryst of his roommate who later committed suicide did not have a problem with his roommate's sexuality, according to testimony on Monday by a key witness in the case.

She testified that Dharun Ravi, who faces the possibility of 10 years in prison, had mentioned that roommate Tyler Clementi was gay but "didn't make a big deal out of it."

Ravi, who set up a webcam on September 19, 2010 that displayed the encounter of Clementi with another man, faces 15 counts of invasion of privacy, witness and evidence tampering and bias intimidation, a hate crime, in Middlesex County, New Jersey, Court.

Clementi, 18, jumped off the George Washington Bridge three days later.

Ravi, 19, is not charged with causing his death, but the case that has raised questions about bullying, teen suicide and privacy in the digital age.

Prosecutors say Ravi intentionally spied on Clementi from another dorm room and intimidated him for being gay. The defense says Ravi behaved childishly but did not commit any crime.

A key witness, Molly Wei, who was originally charged with watching the tryst with Ravi but entered into a plea agreement, testified on Monday that Ravi had briefly mentioned that his roommate was gay but did not consider it an issue.

Wei was among those that saw Clementi kissing another man on the webcam for a few seconds.

"It shouldn't have happened. We saw something we didn't expect to see, and it was just weird," she said.

"I did not expect to see two people in an intimate experience," she said.

Wei said she watched the webcam video stream with Ravi and showed it to a handful of other students when Ravi left the room. She said the second time, the two men were still kissing but with their shirts off.

Wei, whose plea deal required her to testify at Ravi's trial, waved at him briefly from the witness stand. She also must serve 300 hours community service and undergo counseling.

The jury also learned that Clementi had applied to change rooms a day before he committed suicide.

Asked on the university website to list his reason, Clementi wrote: "Roommate used webcam to spy on me/want a single room."

However, the defense successfully argued that the jury should not hear Clementi's reason, saying it was hearsay. The jury only heard that the application had been made.

Ravi, dressed in a suit and tie, talked and smiled with his attorneys. Members of his family and Clementi's family were in court as well.

An acquaintance of Ravi's, Pooja Kolluri, 19, who also saw the video stream, testified that Ravi set up the webcam "to make sure his things weren't touched" after Clementi said he wanted their shared room for a few hours.

Asked by prosecutors if Ravi also wanted to confirm his suspicion that Clementi was gay, she said yes.

Experts say it may be difficult to prove the incident was a hate crime. For such a conviction, prosecutors must prove Ravi attempted to intimidate Clementi for being gay.

Both were freshmen at the time.

Wei was expected to resume her testimony on Tuesday.

(Writing by Ellen Wulfhorst; Editing by Paul Thomasch)