(CBS/AP) NEW BRUNSWICK, N.J. - Tyler Clementi checked his roommate Dharun Ravi's Twitter feed 38 times in the last 48 hours of his life, and took a screen shot of two messages posted there, according to a detective in the Middlesex County Prosecutor's Office.
Gary Charydczak testified Tuesday that Clementi saved screen shots from Ravi's Twitter page, including one that proclaimed Ravi had seen his roommate "making out with a dude," and another where Ravi "dared" his friends to use a web chat program to watch later.
The detective, testifying in Ravi's invasion of privacy and bias intimidation trial, said he learned about Clementi's computer use from examining the hard drive of the laptop that was found in his Rutgers University dorm room.
He displayed the Tweets that he said were saved to Clementi's hard drive under the names "untitled.jpg" and "secondtime.jpg."
Dharun Ravi faces 15 counts against Clementi, who jumped to his death from the George Washington Bridge on Sept. 22, 2010, one day after authorities say Ravi attempted to spy on him.
In testimony earlier Tuesday, Rutgers computer system manager Timothy Hayes told jurors it appears Ravi's computer was used in two video chats on Sept. 21, 2010.
That doesn't prove that Ravi spied on his roommate, but it may bolster the prosecution's case that he was preparing to attempt to spy on Clementi that night.
Authorities say Ravi did use his webcam to see his roommate and another man kissing on Sept. 19 and viewed it from the room across the hall from his own.
Charydczak testified that the computer of dorm resident Molly Wei had a record of a videochat Sept. 19 at about the time she said that she and Ravi briefly used it to see Clementi and the other man kissing.
Prosecutors also have been building the case that Ravi went to the rooms of dorm mates that evening to test his webcam and used Hayes' testimony to corroborate that. He said there was a web chat between his computer and Lokesh Ojha's at 6:58 p.m. that evening, and another with Alissa Agarwal starting 46 minutes later.
Both those students testified that Ravi showed them how they could use a web chat program to see what was happening in his room, although there has been no evidence that anyone used a videochat service to spy on Clementi the night of Sept. 21.
Court documents suggest that Ravi's computer was unplugged before Clementi's guest arrived.