The 21-year-old defendant had been friends with the victim for about four months before he approached him from behind and smacked him in the back of head with a skateboard, causing a serious head trauma, according to court testimony.

The trial of  Kevin Cunningham got underway today in Courtroom 24 with Ventura County Superior Court Judge Ryan Wright presiding.

Cunningham is charged with felony assault with a deadly weapon and causing great bodily injury in an attack that occurred May 18, 2011.

The 22-year-old victim, Jonathan Hill Kennedy, testified that he woke up 10 to 15 seconds after being struck, was driven to the hospital and ended up staying there for a week.

The Simi Valley resident said his skull was fractured in several places.  He suffered bleeding of the brain, and it took 53 staples to close up the laceration, Kennedy testified

During his testimony, Kennedy walked in front of jurors and showed them the permanent scar on his head.

Earlier, prosecutor Richard Simon told jurors during opening statements in the trial that Cunningham accused Kennedy of "forcing" himself on Cunningham's girlfriend and "bashed" him in the head with the skateboard.

Simon told jurors that Cunningham will deny that he struck Kennedy with his skateboard inside Kennedy's garage where the defendant, the victim and two others had been smoking marijuana.

"It was too dark inside the garage. The lights were off and nobody knows who did it," Simon said the defense will claim.

Cunningham's lawyer David Lehr suggested to jurors that Kennedy had marijuana and cocaine in his system before he was struck, questioning what drugs can do to a person's ability to perceive things.

Lehr cautioned the jurors against immediately jumping to conclusions before all the evidence is heard.

Kennedy testified that he met Cunningham about four months before the incident and knew his girlfriend about two months before he met Cunningham.

On the day of the incident, Kennedy said he was inside his garage with two friends smoking marijuana. Cunningham arrived later in the evening with "a serious look" on his face, Kennedy testified.

Cunningham accused Kennedy of forcing himself on Cunningham's girlfriend.

Kennedy admitted on the stand that they both kissed while they were in an empty classroom at Moorpark College. He said he might have inappropriately touched her. However, he adamantly denied "forcing" himself on Cunningham's girlfriend.

"I would never push myself on a girl," he said, adding that he didn't know why Cunningham's girlfriend would say that.

Adding that he told Cunningham, "Come on, dude. You know me. You know I wouldn't do that."

Kennedy said he shook hands with Cunningham. Forty-five minutes later, Kennedy said he went to change the station on his radio when he was struck.

"I was sitting on my couch and my head was ringing," Kennedy testified.

He said his two friends who had been inside the garage told him that Cunningham "smacked" him on the head with the skateboard and left.

On the stand, Kennedy said he sold small quantities of drugs and uses medical marijuana because it relieves his anxiety and stress and when he doesn't use marijuana, he gets "restless leg syndrome."

Kennedy admitted having sex with Cunningham's girlfriend five or seven times, and twice when Cunningham was there.

"They just started and invited me in," Kennedy testified.

Kennedy said he still uses drugs, including marijuana.

"I feel normal when I smoke. I feel abnormal when I don't smoke," he testified.

The trial resumes this afternoon.