A composed and often-smiling Clara Harris described a marriage that was a solid, loving relationship until David Harris began changing last spring.
"We were best friends," Clara Harris said Wednesday. "We were very much in love."
She took the stand against the advice of her attorney, reports CBS News Correspondent Lee Cowan.
She said she and her husband were "mature people" who had each survived divorce, adding: "We felt like there was no better couple than us."
The 10-year marriage ended July 24 in the parking lot of a suburban Houston hotel, when she allegedly ran him down with her Mercedes-Benz. Harris is charged with murder for the death of her 44-year-old orthodontist husband.
She claims the death was accidental and that she shouldn't be charged with murder. Prosecutors say it was intentional.
Harris spent about 90 minutes on the stand Wednesday before a lunch break.
Then her lead attorney George Parnham walked out of court only to collapse in a hallway, putting a halt to the proceedings before Harris ever got a chance to explain her side of what happened the night she ran her husband down.
He was hospitalized as a precaution, though colleagues said he was doing well Wednesday afternoon.
District Judge Carol Davies said testimony would resume Friday morning.
Wendell Odom, one of Parnham's partners, attributed the possible fainting spell to a combination of flu and stress.
"George is all right and the trial will continue as soon as we get him back," Odom said.
In her testimony, Clara Harris described how the couple met as associates at a dental office, their eventual marriage, birth of twin sons after five years of trying to have children and the establishment of their separate practices.
Then things started changing around April 2002.
"He was a little bit more stressed. He was a little bit more intolerant of the boys," she said, although at the time she attributed some of the stress to the construction of his new orthodontic practice.
He was spending less time with his family and more time to himself, she said.
An employee told Clara Harris on July 16 that her husband had been seeing receptionist Gail Bridges. The next morning, Harris said her husband told her he had been modestly intimate with Bridges.
A week later, she allegedly ran the husband down after catching him with the other woman.
If convicted, Harris faces up to life in prison. If jurors determine she acted under the legal definition of sudden passion, they could consider a lighter sentence of two to 20 years in prison.