Harris, who had remained stoic during her verdict on Thursday, slumped in her chair crying as the judge read her sentencing. The 45-year-old dentist had faced up to life in prison if the jury had ruled she had not murdered her husband as a crime of "sudden passion", or as little as probation.
Harris' lawyer George Parnham had requested probation, saying the Harrises' twin sons need their mother, whom he described as "a good mother and a good wife."
Parnham argued that Clara Harris acted out of sudden passion. Parnham suggested that the victim himself would have wanted his wife to receive probation and continue raising their twin 4-year-old sons.
David Harris' father, mother and brother "don't want those boys ripped away from the last parent that they have on this Earth," Parnham said. "What I want you to think about is what, based on all of the evidence in this case, what would David want?"
Prosecutor Mia Magness, however, said Harris was using her sons as a "shield" to gain probation. She urged prison time, though she made no specific recommendation about the length of a sentence.
"She ought not get credit for making herself a single parent," the prosecutor told jurors before deliberations began. "She did that when she made the choice to kill their dad. It's not fair to dangle those two boys out in front of you the way that she has."
Jurors deliberated for six hours before returning with their verdict on the sentence. The same nine-woman, three-man jury deliberated about eight hours before returning the murder conviction.
CBSNews.com Legal Analyst Andrew Cohen says Texas showed too much mercy towards the Mercedes Muderess.
Harris' tears, "certainly didn't look like tears of joy but they should have been. A 20-year prison term for a first-degree murder conviction in Texas is a pie-in-the-sky legal result if I have ever seen one,'' he said.
"If Harris were a man we would have seen a life sentence in this case. If Harris were a minority defendant we would have seen a life sentence in this case. But Clara Harris is a weepy, white, professional woman, someone whose marital troubles generated a lot of sympathy in and out of court. So she will walk out of prison in about 10 years or so (with time off for good behavior and parole)," says Cohen.
Clara Harris was convicted Thursday of murder by the jury that rejected her claim she was aiming for his lover's car.
Jurors deliberated for eight hours over two days before reaching the verdict. Two of them cried as state District Judge Carol Davies read it in court.
The trial was front-page news in Houston and included dramatic testimony from Harris, her romantic rival and her stepdaughter, who was in the car that day and told jurors her stepmother sped toward her father as he desperately tried to get out of the way. The parents of the victim, David Harris, took the stand, too — to testify in support of their daughter-in-law.
Harris insisted the death last July was an accident and that she only wanted to damage the black Lincoln Navigator belonging to her husband's receptionist turned lover, Gail Bridges.
She told jurors she wanted to save her 10-year marriage after learning of the affair. She said she quit her job, had sex with her husband three times a night, cooked his favorite meals and hired a personal trainer.
She also testified she even went to a tanning salon and scheduled liposuction and breast enhancement surgery to make him happy, only to catch him in a tryst with Bridges at the same hotel where the Harrises were married on Valentine's Day 1992. David Harris was killed in the hotel parking lot moments later.
Perhaps the most powerful witness was David Harris' daughter, 17-year-old Lindsey Harris, who was in Mercedes.
"She stepped on the accelerator and went straight for him," Lindsey Harris told jurors. "He was really scared. He was trying to get away and he couldn't."
The teenager said she never thought her stepmother would act on a comment that she could kill David Harris and get away with it. She said her stepmother made the remark just after finding him with Bridges.
"I knew she had killed my dad," Lindsey Harris testified. "She said, 'I'm so sorry. I'm so sorry. It was an accident.'
"She knew what she did and she wasn't sorry."
The death came a week after David Harris confessed to his nearly three-month affair with Bridges. The Harrises, who also were business partners, then spent an evening at a bar talking about their relationship.
According to bar napkin notes kept by Clara Harris, David Harris thought his wife was overweight, dominated conversations and was a workaholic, all in contrast to Bridges. While he gave his wife higher marks for "prettier" hands, feet and eyes, he described his 39-year-old receptionist, a former beauty queen, as "petite" and "the perfect fit to sleep with, holding her all night."
Clara Harris said that remark stunned her.
"I couldn't believe he could sleep holding her all night because we had never slept like that — never," she testified.
Recalling the day of the accident, Clara Harris wept as she said "everything seemed like a dream." She confronted the lovers in the hotel lobby and brawled with Bridges before returning to her car.
"I was in so much pain; it was a physical pain that I was feeling. I wasn't thinking anything," Harris testified. "Suddenly, I thought about smashing my car against her car and then I (picked) up speed."
But she denied trying to run him down and said she didn't recall hitting him. "I think I closed my eyes" just before impact, she testified.
Harris said she snapped out of her daze as her stepdaughter screamed for her to stop. She got out and saw her husband lying on the pavement, blood streaming from his ears and mouth.