Raleigh, N.C. — An FBI agent testified Tuesday that Brad Cooper logged on to his Cisco work computer four times between 10 p.m. and midnight the night before his wife, Nancy Cooper, was killed – the same time the defendant has said he was asleep with his young daughters.

Gregory Johnson, a special agent with the FBI's Computer Analysis Response Team, said he also found evidence of Internet activity but that he wasn't sure if someone was using the Internet or if it was automatic computer updates from the Web.

Computer logs also showed online activity more than half a dozen times on the morning of July 12, 2008, starting at 6:52 a.m., Johnson said, but he did not say what kind of activity.

Brad Cooper, 37, is accused of killing his wife in their Cary home in the early hours of July 12, 2008, and dumping her body in a drainage ditch in an undeveloped subdivision.

A man discovered the body two days later while walking in the area near Holly Springs Road and Fielding Drive just outside Cary's town limits. An autopsy found Nancy Cooper, 34, had been strangled.

Defense attorneys Howard Kurtz says that Brad Cooper returned home from a neighborhood party around 8 p.m. on July 11, 2008, put his daughters to bed and fell asleep with them. He woke up sometime after midnight to the sound of his wife coming home from the party.

Later that morning, he was on his computer, checking email, when she went for a run, Kurtz says. Nancy Cooper never returned home.

Kurtz, on cross-examination, questioned whether the computer was compromised, noting that it was on for 27 hours after police seized it and that 690 files were changed during that time, some as a result of automated Windows operating system updates.

Johnson said he didn't know why or how the files were modified and that he was aware of the defense's allegations but did not look into them because he was not asked to do so.

On redirect from the state, he said, found no indication that they had been tampered with.

"They were all the result of normal operation a computer connected to the Internet, especially to a system like Cisco's," Johnson said.

Johnson also said that he found no evidence to suggest that the computer was used to generate a phone call from the Cooper home that defense attorneys have said proves Brad Cooper didn't kill his wife when prosecutors think he did.

"You found no such evidence of that?" Kurtz asked.

"I did not," Johnson replied.

Earlier Tuesday, Superior Court Judge Paul Gessner suppressed testimony that Brad Cooper bookmarked a website in February 2008 about suicide by asphyxiation – testimony Kurtz said he objected to because it is prejudicial and had no relevance to the murder case.

"This is simply a way of making him appear in the most negative light possible," Kurtz told Gessner.

But Wake County Assistant District Attorney Boz Zellinger called the testimony "extremely relevant," Brad Cooper would have known about asphyxiation and that he bookmarked the site, even though he testified in a deposition that he was not suicidal.

Kurtz said his client admitted to visiting a website about fathers who have lost custody of their children committing suicide.

Tuesday marks the 24th day of testimony in the prosecution's case. Defense attorneys have yet to present their case.

They contend that Cary police ignored evidence that could have helped them find Nancy Cooper's killer, including testimony from several people who said they thought they saw her jogging that morning.

Testimony of Johnson and other witnesses related to the FBI could not be posted on WRAL.com because of Gessner's order that prohibits them from being recorded.