Charlottesville, Virginia (CNN) Shortly before James Fields rammed his car into counterprotesters at a white nationalist rally, he had asked some of his fellow protesters out to lunch.

Hayden Calhoun and his girlfriend declined, Calhoun testified Wednesday.

Twenty minutes later, Fields plowed into the counterprotesters, killing a 32-year-old woman and injuring more than a dozen others.

Those were some of the latest revelations from Fields' murder trial Wednesday. The 21-year-old is charged with first-degree murder for the death of Heather Heyer , who was protesting against last year's "Unite the Right" rally.

Both the prosecution and defense agree that Fields drove into the crowd of counterprotesters. But while the prosecution believes Fields had malicious intent, the defense team said he feared the counterprotesters and acted in self-defense.

If convicted, Fields could be sentenced to life in prison. He also faces eight other counts related to eight people injured in the crash, as well as one count of failing to stop at an accident involving a death.

The defense called Calhoun to take the stand Wednesday. Calhoun said he and his girlfriend attended the rally on August 12, 2017, and spent part of the day with Fields, whom they had just met that day.

Calhoun testified that Fields was calm and seemed tired.

Under cross-examination, Calhoun testified that the only interactions he and Fields had with counterprotesters were verbal, not physical. Calhoun said counterprotesters didn't attack them or throw anything at them.

Footage of the crash showed Fields' Dodge Challenger careening into pedestrians, sending some airborne.

On Wednesday, Trooper Clifford Lee Thomas, a crash reconstructionist for the Virginia State Police, testified that Fields had accelerated to a maximum of 28 mph before crashing into a Toyota Camry.

The impact caused the Camry to go from zero to 17 mph in 150 milliseconds.

Charlottesville Police Detective Steven Young and Calhoun's girlfriend, Sarah Bolstad, also testified before the court took a lunch break.

Bolstad said she met Fields when they were turned away from McIntire Park by police. She testified she and Calhoun were approached by Fields and another man, who suggested they travel together as there is safety in numbers.

"I felt really comfortable with them," she said. She added that Fields "didn't seem angry" and "seemed normal."

She never saw Fields during times when bottles were being thrown, she told the court.