A woman accused of repeatedly running over her cheating husband with her Mercedes-Benz could not have killed him the way prosecutors claim, the defense's first witness testified Friday.

Prosecutors say Clara Harris circled around and repeatedly hit David Harris with her speeding car, but collision expert Steve Irwin said that while she made tight circles around the body, she hit it only once.

He said he used skid marks and other evidence to reconstruct the car's speed and route, also factoring in the vehicle's 20-foot turning radius.

"If you get in this car and make a turn and rocket left you can never get back to that mark," Irwin said, describing blood left on the pavement where David Harris' body landed after he was hit the night of July 24.

Under cross-examination, Irwin acknowledged that Harris' 5-foot, 9-inch frame could have extended significantly beyond the blood spot.

"What you're really telling this jury is ... you can't tell them she never ran over that body again because you don't know where the body was," prosecutor Mia Magness said.

"Fair enough," Irwin replied.

Prosecution witnesses have disagreed on the number of times Harris was hit. One said twice, another said five times.

Clara Harris, 44, is accused of running down her orthodontist husband, also 44, in a hotel parking lot after finding him with another woman. Defense attorneys contend his death was accidental.

Irwin told jurors Clara Harris struck her husband and his body fell on the hood of her car. The body then fell from the hood and was rolled over by the driver's side wheels, he said.

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.