HONOLULU -- The attorney for murder suspect Kirk Lankford began piecing together his defense in court on Thursday.

Lankford claims Masumi Watanabe killed herself when she suddenly jumped out of his truck.

As a criminal defendant, Lankford does not have to prove his innocence, just cast enough doubt on the state's case to sway a jury.

So, the best he offered on Thursday was an expert opinion that his story makes sense.

Lankford is claiming he only slightly injured Watanabe when he struck her with his truck, but then she apparently panicked as he looked for help, leaping from his truck at nearly 40 mph and striking her head on a rock.

"She could have torn blood vessels. She could have torn the brain stem," forensic expert Dr. James Naven said.

Naven was hired by the defense. Lankford told him that Watanabe hit a 125-pound rock, tumbled for a while and had major head injuries.

"(Lankford said) that she had a hole in the head. He could see bone in the bottom of the hole and something darker in hole than blood," Naven said

Naven said the scenario Lankford described could happen. The prosecutor pointed out that because Watanabe's body has never been found to examine, all the facts came from Lankford.

"You didn't pass any judgment on their accuracy or veracity you just took them at face value?" the prosecutor asked Naven.

"That's true," Naven said.

The defense is also trying to weaken prosecution evidence that contradicts Lankford's story. One witness said she saw men other than Lankford harassing an Asian woman on the road that day.

A Foodland executive said the clocks in the company's registers might be off by a few minutes. So, Lankford may not have bought cleaning supplies on his visit.

A police technician explained why no blood evidence was found where Lankford said he put Watanabe.

"It was such a small area, it didn't seem like a body could fit in it," Honolulu Police Department Evidence Technician Walter Fung said.

Besides Lankford himself, the defense only has one more witness. None of his friends or family will testify. That is because if one of them claims he is incapable of violence the prosecutor may be allowed to bring up a prior, unproven allegation Lankford once tried to assault another woman.

The trial resumes after taking next week off.