[The biased expert: An unknown quantity].

Academic publications have so far hardly paid any attention to the topic of biased medical experts or expert opinions. This is the first attempt to systematically describe and analyze the issue, drawing on the author's many years of giving expert opinions as a neuropsychiatrist on matters relating to social legislation and civil law. In addition to dealing with questions of definition, this article outlines the features of biased expert opinions, particularly focusing on the role of insurance and private experts. Finally, proposals are made to initiate a discussion on how to prevent biased expert opinions and improve their registration.