OAKLAND, Calif. -- A judge Wednesday denied a defense request that Hans Reiser, who is on trial for killing his estranged wife, be allowed to testify about the lifestyle of a former boyfriend of Nina Reiser who was allegedly "heavily into drugs and sadomasochism."

In a short but heated hearing outside the presence of jurors, defense attorney William DuBois said he wanted to be allowed to show that Sean Sturgeon, an Oakland man who was a friend of Hans and had an affair with Nina, was "heavily into drugs and sadomasochism."

DuBois said that would illustrate that "Nina's deportment was not that of the perfect mother that's been portrayed by the prosecution in this case."

He also said Sturgeon had a key to Nina's rental house in Oakland as recently as January 2006.

Prosecutor Paul Hora accused DuBois of trying to just "trash her (Nina) again" and said there's no evidence Nina would have abandoned the couple's two children.

"I've never said Nina was a perfect person, but she didn't leave the kids," Hora said. "The issue is whether he (Hans) murdered her (Nina) or if she abandoned the children."

Alameda County Superior Court Judge Larry Goodman, noting that the issue of Sturgeon's character was raised in pretrial motions, told DuBois that he won't allow DuBois to ask Hans Reiser about Sturgeon's alleged sadomasochism when Reiser resumed his testimony.

Goodman said evidence about sadomasochism is more prejudicial than exculpatory, using legal jargon for evidence that proves a defendant is innocent.

But the judge did allow testimony about the affair.

"I think that her reason for having an affair with Sean was as much to upset me as to have an affair with Sean," Reiser told the court.

Du Bois asked if he was upset.

"Not as upset as she wanted me to be," said Reiser. "I forgave her and we decided to continue on with the marriage."

He said he still cares for her.

"I enjoy her presence," he said. "I've always liked spending time with her. And we have two wonderful children."

Nina Reiser, who was 31 at the time, was last seen alive on Sept. 3, 2006, when she dropped off the couple's two children at the house at 6979 Exeter Drive where Hans Reiser lived with his mother.

Hans and Nina Reiser married in 1999 but she filed for divorce in August of 2004 and was awarded legal custody of the children, although he was allowed to have them stay at his house several days a week. Their divorce never was finalized.

The body of Nina Reiser, who was born in Russia and was trained as a physician there, has never been found, despite extensive searches in the Oakland hills and elsewhere. But in October of 2006 Hans Reiser was charged with murdering her because prosecutors believe that DNA and blood evidence proves that he killed her.

He has pleaded not guilty to the charges against him.

DuBois has said that he thinks Nina Reiser may still be alive and in hiding somewhere, possibly in Russia.

The couple's children, Rory and Nio, are living in St. Petersburg, Russia, with Nina's mother, Irina Sharanova.