Dejon Baskin is accused of shooting and stabbing his ex-wife and her family members three years ago.
Baskin doesn't deny the violent attacks. He and his attorney claim he doesn't remember it - they blame PTSD from military service.
But prosecutors say there was no substantial diagnosis of PTSD. They claim he went after his estranged wife and her family, intending to kill them, and failed.
Baskin told jurors about his upbringing - about living in 12 different houses before he entered sixth grade. He said he was sexually assaulted as a child and suffered from mental disorders.
All of this before becoming a Marine, before he was accused of slashing his ex-wife's throat.
"He never attempted to kill anyone. He was in a blackout type situation, a flashback type of situation, Sgt. Baskin never attempted to take anyone's life that's obvious," Eric Schweitzer, Baskin's defense attorney, said.
It was July of 2009 when Reedley police responded to dozens of 911 calls. One of them was from Rachel Baskin, Dejon's estranged wife.
Rachel Baskin survived, although her throat was slashed.
Dejon Baskin told jurors Wednesday afternoon he's a "changed person" after hearing her testify about the attack.
"I'll never be able to forget these demons of regret. She won't, I won't. I won't be able to explain to my little girl, what I did, or why I did it," Baskin said.
Prosecutors say Baskin had had an affair, was abusive and didn't pay child support.
Baskin is expected to be back on the stand again Thursday as the defense phase of his trial continues.