A German sports doctor on trial for masterminding an international doping network for athletes admitted on Tuesday to helping athletes with blood doping for years but said he made no profit. The defendant, identified in Germany only as Mark S., is on trial, facing multiple charges in relation to helping at least 23 athletes from eight countries gain an unfair advantage over several years.

“I did not make a profit from doping,” he said in a statement read by his lawyers in court. The defendant also said he never put the athletes’ health at risk but did admit to blood doping.

“For me it was always important that there was no damage to the athletes’ health.” The case is a result of “Operation Bloodletting” under which police raided the Nordic Ski World Championships in Austria in February 2019 and arrested athletes just hours before the start of an event. Mark S. was arrested in Germany.

Prosecutors say he was behind performance-enhancing blood transfusions mostly for cross-country skiers and cyclists. They believe he was involved in the practice from at least the end of 2011.

Four other suspects are on trial accused of helping him with the collection and supply of blood. If convicted, the doctor could be put behind bars for between one and 10 years. The trial is set to continue until at least mid-December.

The trial that started earlier in September continues and a verdict is expected in the coming months.