Dr. David Van de Loo of Eau Claire described his education and professional standing for the jury. He maintains there were legitimate medical reasons for all genital checks he performed on his patients.
But Van de Loo testified there was one exam that left a patient upset, WDIO-TV reported.
"I was thinking that it was important to make the diagnosis and, you know, I should have stopped and thought about how he was perceiving it," Van de Loo said. "I thought I was communicating, but I should have communicated more. I should have talked to him. I should have called his parents."
Prosecutors contend Van de Loo had no medical reason to touch the 15 male juvenile patients' genitals. The 61-year-old faces 16 sexual assault-related felony charges.
The defense argues that the boys misconstrued what the doctor was doing during exams.
The longtime adolescent and sports medicine specialist at Mayo Clinic Health System in Eau Claire was fired on Sept. 12, 2012, after allegations of sexual assault surfaced.
The trial was moved from Eau Claire County to Douglas County because of pre-trial publicity.