When a woman found her husband cheating on her, she ran him over with her Mercedes-Benz and "turned her $70,000 vehicle into a 4,000-pound murder weapon," prosecutors said in court Thursday.

Clara Harris, a 44-year-old Houston dentist, is accused of killing her husband in a hotel parking lot July 24 after confronting him and another woman in the building lobby.

During opening statements at Harris' murder trial, prosecutor Mia Magness told jurors that Harris gave her husband, David Harris, an ultimatum, ordering him to choose between her and his mistress, Gail Bridges. When he chose Bridges, Magness said, she got into her car and purposely ran him down.

"The evidence will show you she intentionally and knowingly hit him and didn't stop. She did it again and again and again," Magness said.

But Harris' defense attorney, George Parnham, described her as a woman who only wanted to keep her family together but "loses it" after going to the hotel where she had married David Harris a decade earlier and finding him with a mistress.

As Clara Harris wept, Parnham described her as a loving mother and devoted wife who was heartbroken after finding out her husband had misled her and would not end his affair. Harris has said her husband's death was an accident.

"I want you to reserve your judgment until you hear evidence about what physically happened in that parking lot ... whether or not Clara Harris intentionally caused the death of David Harris," Parnham said.

On July 24, Clara Harris confronted her husband and Bridges when they emerged from an elevator at the hotel. She fought with Bridges and ripped off some of her clothes.

A hotel employee testified Thursday that as Clara Harris was escorted from the hotel, David Harris yelled at her: "It's over! It's over! It's over!" Clara Harris then calmly got into her silver sedan as David Harris walked Bridges to her vehicle, Evangelos Smiros testified.

She drove her car at a high rate of speed toward them, Smiros said. "I banged on her trunk and said, 'Stop! Stop! You're going to hurt someone,"' Smiros testified, saying he watched helplessly as Clara Harris hit her husband three times.

Clara Harris' 17-year-old stepdaughter, Lindsey, was a passenger in the car. She tried to get out but couldn't until the car came to a stop.

"'You killed my dad,"' Smiros said Lindsey Harris told her stepmother afterward.

Another hotel employee, Blake Doran, recalled Clara Harris apologizing to her husband and telling him how much she loved him.

The two witnesses were among four hotel employees who testified Thursday. One employee said he saw Clara Harris circle and hit her husband five times, while another said she only struck him twice.

If convicted, Clara 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.

Evidence is expected to include a videotape taken in the hotel parking lot by a private investigator Harris hired to follow her husband. Jurors also are expected to hear from Lindsey Harris.