Mark Schmidt, a German doctor accused of being part of an international blood doping ring, has claimed he wanted to protect athletes as his court case continues.
Schmidt was arrested last year after police carried out raids at the International Ski Federation Nordic Ski World Championships in Seefeld in Austria and in the German city Erfurt.
At least 23 athletes are believed to have been involved in the blood doping network in Germany and Austria.
Schmidt and four co-defendants, who have been accused of aiding him, have reportedly been accused by prosecutors of helping the athletes undergo blood transfusions.
According to Agence France-Presse, Schmidt read out a statement claiming he had been trying to protect athletes he worked with.
Schmidt reportedly said he had not initiated the doping network but had been meeting demand, having received requests from athletes.
The doctor also admitted he never thought he could face prison.
"[I] completely misjudged the punitive framework," Schmidt said, according to Agence France-Presse.
"I never thought that I would be threatened with imprisonment."
The doctor said he asked for €5,000 (£4,600/$5,900) a year from athletes for his services, although an email reportedly revealed he had charged three Estonian athletes €11,500 (£10,300/$13,700) each.
Chief prosecutor Anne Leiding told the Munich District Court in September that the defendants had been helping athletes boost performance from "the end of 2011 at the latest".
Schmidt admitted earlier in the trial that since 2012 he had been using doping methods and given prohibited substances to athletes.
Operation Aderlass was launched last year, which led to the police raids in Seefeld and Erfurt.
The raids followed revelations made by Austrian skier Johannes Dürr about blood doping in an ARD documentary.
Dürr was banned for life from the sport after admitting to blood doping.
Around 40 blood bags and other items associated with doping were reportedly seized during the raids in Germany.
Blood was said to have been taken around the world to Germany, Austria, Italy, Sweden, Finland, Estonia, Croatia, Slovenia and the American state of Hawaii.
Several athletes have faced sanctions for involvement in the Operation Aderlass blood doping scandal.
Schmidt and the co-defendants could face jail for up to 10 years if found guilty.
It follows anti-doping legislation introduced in Germany in 2015.