Testimony began last Thursday, and in the first few days jurors have heard an involved account. They learned that Mrs. Nyce had carried on a yearlong affair with the landscaper, who had planted trees in their yard, and that Dr. Nyce took steps to put a stop to it.

On Wednesday, the landscaper, who said he had used several aliases, testified that he had, indeed, had an affair with Mrs. Nyce. He also testified that Dr. Nyce, 55, had called him on his cellphone in July 2003 and threatened him. "He said, 'You put your hands on my wife again, you're going to be a dead man,"' Mr. DeJesus said.

Prosecutors contend that Dr. Nyce confronted and viciously attacked his wife, repeatedly smashing her head into the concrete floor. They say he then stuffed her behind the driver's seat of her Land Cruiser and steered the car with an ice pick down to the half-frozen Jacobs Creek, where he left her. He faces two counts, first-degree murder and trying to cover up a crime. He could face life in prison if convicted.

Dr. Nyce's lawyer, Robin K. Lord, says that the death of Mrs. Nyce was "an accident," and that she will prove that in court. She says that Dr. Nyce has been accused of a crime he "did not commit" and that she will show that his wife, who she says repeatedly cheated on him, tried to attack him first. She declined to elaborate on her strategy.

"We know what occurred in that garage," she said in a recent interview, "and hopefully the jury will agree, when it's all said and done."