Gwyneth Paltrow is being sued by a 76-year-old retired optometrist, Terry Sanderson, over a 2016 ski accident in Utah.
Sanderson claims that Paltrow crashed into him violently at a resort in Utah and then skied away.
He is seeking $300,000 in damages due to lasting injuries.
Paltrow has filed a countersuit, arguing that Sanderson is the one who hit her.
The daughters of Sanderson are testifying in court on Thursday.
The case will come down to who was above the other on the mountain.
Paltrow claims that there is video evidence of the incident, but it has not been presented in court.
The burden of proof in this civil case is preponderance of evidence, which means anything slightly over 50 percent.
The credibility of each party and their witnesses will be crucial in determining the outcome of the case.