Richmond's attorney, Walter Madison, challenged whether Westlake was trying to right a wrong through his testimony.
"I felt a lot of regret, difficult to face my family knowing they knew what I had done," Westlake testified.
Anthony Craig, 18, also testified Friday that he saw Richmond digitally penetrate the girl in the basement.
"She wasn't moving. She wasn't talking. She wasn't participating," he said.
Craig also admitted taking a nude cell phone picture of the girl while she was in the basement and showing it to friends.
"It was stupid," he said.
In earlier testimony, teens who attended some of the booze-soaked parties testified the girl appeared to be drunk, stumbling and slurring words. But on cross-examination some said she seemed able to walk and answer questions.