Book excerpt: Medical confidentiality is universally recognised as a value worth protecting. However, difficulties arise when confidential medical information becomes relevant in the context of crime prevention and criminal prosecution. Should medical confidentiality be upheld where the physician holds information which is essential for the investigation of a serious crime; for establishing the truth in a criminal trial; for an accused’s defence; or for the prevention of a criminal offence? And according to which criteria should such decisions be made? Based on an examination of different approaches in medical ethics and a comparison of the relevant law of France, Germany, England and Wales and the US, this book analyses how a balance of the competing interests can best be struck.