In Germany, paternity testing can be ordered by a judge as well as by private persons. In the case of private counselling, the expert has the duty to inform the parties on all medical, legal and ethical aspects. Informed consent must be given by each individual included in an exploration of family relationships. Due to the rapid progress of DNA typing in even minute amounts after polymerase chain reaction amplification, genotypes of short tandem repeat systems can be elicited by extraction from single cells. Therefore, the number of unlawful investigations of paternal relationships is steadily increasing. Here the requirements for paternity testing laboratories and sanctions for unlawful exploration of a person's genotypes are discussed. A new Federal law should be drafted.