OAKLAND, Calif. -- During a full day on the witness stand computer engineer Hans Reiser did not express any concern about the disappearance of his estranged wife Nina 18-months ago and instead said Monday that marrying her was a mistake.

While being questioned during a trial that charges him with Nina's murder, Reiser, 44, had to think hard when his lawyer William DuBois asked him if he and Nina fell in love after they met in St. Petersburg, Russia, in January of 1998.

Reiser said, "Um, yes, but in retrospect I should have waited until I found someone I loved more deeply than I loved her. I loved her, but not enough to marry her, and that was a mistake."

Asked by DuBois if he thinks Nina loved him, Reiser said, "When you look at it objectively, it's hard to come to the conclusion that she loved me."

"I think Nina loves attention and needs to be loved but does not herself love," he added.

When prosecutor Paul Hora asked that Reiser's answer be read back, the court reporter in the case quoted Reiser as saying Nina "did not herself love."

Reiser corrected the tense used by the reporter and again used the present tense, saying Nina "does not love," possibly implying that he thinks Nina is still alive.

He added that Nina "is not capable of love."

Reiser also said that he married Nina partly as a favor to her because her visa was expiring.

Nina Reiser, who was 31 at the time, disappeared on Sept. 3, 2006, after 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 is hiding somewhere, possibly in Russia.

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

DuBois spent most of Monday asking Hans Reiser about his background, such as his admission to the University of California, Berkeley at the age of 15 and the 20 years he spent developing a computer file system called ReiserFS that was eventually was incorporated into the Linux operating system and ultimately was profitable after many lean years.

But DuBois started the day by asking Reiser about the last day that Nina was seen alive.

Reiser said Nina brought the couple's children to his house at 6969 Exeter Drive about 2:20 p.m. on Sept. 3, 2006.

He said he and Nina prepared some food for the children, then the children went downstairs while he and Nina talked as they sat on a black leather couch in the living room on the main floor.

Speaking in a calm and confident tone, Reiser said he told Nina that he no longer would pay her $1,000 a month in child support, that he wanted her to pay him alimony and that he wanted legal custody of their children.

Reiser said Nina refused all those demands but told him he could take the children to his dentist instead of her dentist. He said Nina went to "one of the most prestigious dentists in the Bay Area" but he used a dentist in Oakland who "does good work and is inexpensive."

Reiser said Nina also told him that she planned to marry or at least move in with Anthony Zografos, an Oakland man whom she'd been dating for many months.

He told DuBois that didn't upset him because he thought "Anthony was a good influence on her" and "he urged her to be reasonable" in the divorce case.

Reiser said that after about an hour of talking with Nina she told him, "Hans, I have to go."

He said he wanted to talk some more because, "I wanted to finish convincing her of all the points in the divorce.

However, Reiser said Nina insisted on leaving, said good-bye to the children, walked out the front door, got into her Honda Odyssey mini-van and drove away.

Asked by DuBois if he ever saw Nina again, Reiser said, "No, I did not."

Reiser said he met Nina through a marriage agency in St. Petersburg, where he spent much time while working with his file service company, which is called Namesys Inc.

He said he went to Russia both because he found computer programmers who would work for him for cheap wages and because "the women in Russia are beautiful."

Reiser said he dated many women in Russia before he met Nina and brought a woman named Yelena to live with him in Sunnyvale for about six months, probably in 1997, on a fiancee visa but ultimately decided not to marry her.

Asked by DuBois if Nina was the most beautiful woman he ever dated, Reiser said Nina was the most "mentally attractive" woman he ever dated.

Asked if Yelena was more beautiful than Nina, Reiser said, "I'd rather not say."

Reiser said Nina "has extraordinary people skills, is very perceptive and in all the stereotypically female aspects of her mind she's exceptionally gifted."

Reiser's trial, which began on Nov. 6 and isn't expected to conclude until some time in April, won't meet on Tuesday because a juror has a prior commitment.

DuBois will continue his direct questioning of Reiser on Wednesday.

Hora may not be able to begin cross-examining Reiser until March 17, as DuBois plans to interrupt Reiser's testimony on Thursday by putting a defense DNA expert on the witness stand and the judge in the case will be on vacation next week.