DENVER — An assertive Taylor Swift told a Denver jury on Thursday that there was no question she was intentionally groped in 2013 by a radio host who is suing her because, he says, she falsely accused him and cost him his career.

Ms. Swift said that the former host, David Mueller, was trying to evade responsibility for his actions and that whatever trouble he finds himself in, he had brought on himself.

“I’m not going to allow you or your client to make me feel like this was my fault, because it isn’t,” Ms. Swift told Mr. Mueller’s lawyer, Gabriel McFarland, testifying with confidence, irritation and flashes of humor during an hour on the stand.

She repeated her assertion that Mr. Mueller put his hand up her dress and grabbed her bottom as he posed for a photograph with her before a concert in Denver on June 2, 2013. Mr. Mueller sued in 2015, saying Ms. Swift’s account had led the Denver radio station KYGO to fire him, and has kept him from working in the industry. Ms. Swift then countersued, accusing Mr. Mueller of assault and battery.