The 48-year-old vascular surgical specialist is accused of rape, sexual assault and causing grievous bodily harm against women who had volunteered to partake in a study.
The man was arrested in August after an intern at the Bamberg Hospital in Bavaria took part in his study.
She said he administered an injection without her permission. After her participation, she went to another hospital for blood tests and found that the tests he was supposed to have done were not carried out.
Until now, the doctor had denied any wrong-doing, maintaining that all the evidence against him was collected honestly for valid medical reasons.
Following the accusation, police then uncovered a trove of photographs at the doctor's home and office showing the violation of several female patients.
State prosecutors said that the 13 alleged victims are between the ages of 17 and 28 and all partook in the supposed study. Ten women were patients, two were temporary workers in the hospital and another was a personal friend of the doctor.
Evidence includes 70 witnesses, expert testimony and a number of videos and photos "that reflect the facts of the case", said Bardo Backert, the state prosecutor handling the case.
The soonest the case will come to trial is March.