Paul Kaeo killed his estranged wife’s boyfriend in Maili two years ago because the boyfriend beat and threatened his wife and also threatened to kill him, his lawyer said Thursday.

But Kaeo’s wife and brother-in-law said it was Kaeo who made death threats.

Kaeo, 46, is on trial in state court on a second-degree murder charge in the May 8, 2009, beating death of Charles Kahumoku Jr.

Police recovered a 2-foot-long metal reinforcing bar, or rebar, at the scene.

City paramedics said Kahumoku was unresponsive when they arrived and displayed no vital signs.

The Honolulu Medical Examiner said Kahumoku, 49, died of blunt force trauma to the head. He also had a blood alcohol content of 0.221, more than twice the legal threshold for drunken driving.

Debbie Kaeo testified Thursday that she started dating Kahumoku in November 2008 and moved in with him a few months later. She said her husband continued to live at her mother’s Hakeakea Street home with her mother and brother.

She and Kahumoku are first cousins. However, Circuit Judge Karen Ahn has so far prohibited Paul Kaeo’s lawyer from telling that to the jury.

On the day of Kahumoku’s beating death, Debbie Kaeo said, she went to her mother’s home to help her brother and husband prepare food for a relative’s baby shower the next day. When Kahumoku showed up to take her home, she said, her husband pushed her to the ground and went after Kahumoku with the rebar.

"I going kill him," Kaeo threatened at one point, she said.

Kaeo said Kahumoku never got out of the truck. She said she did not see her husband strike Kahumoku.

Debbie Kaeo testified she told her husband that Kahumoku beat and threatened to shoot her. But Debbie Kaeo and her brother, Calvin Baker, also said Paul Kaeo threatened to kill Kahumoku.

Paul Kaeo’s attorney Randall Hironaka said his client feared that if his wife went with Kahumoku, he was going to continue to beat and threaten her.

She has since moved out of state.

During her testimony, the city prosecutor provided two plainclothes investigators for extra security because she fears retribution from both her and her husband’s families, said Adrian Dhakhwa, deputy prosecutor.