Approximately 1% of the general population suffer from fetal alcohol spectrum disorder (FASD) making it one of the most prevalent biological causes of mental retardation and/or other performance deficits. This article discusses the forensic significance of FASD. In our view, FASD works not only as a primary risk for mental retardation but also as a precondition for secondary disorders, such as attention-deficit hyperactivity disorder, conduct disorders, and substance abuse. Other criminogenic risks, such as failure at school, insufficient vocational training, unemployment and homelessness, are associated with FASD. The association of FASD with delinquency is discussed differently in the literature. In older studies, a strong relationship was emphasized but in more recent studies relatively weak correlations were found; however, FASD can be regarded as a risk for delinquency as long as it works as a risk for mental retardation and/or a precondition for other disorders. For forensic psychiatry FASD becomes important for §§ 3 and 105 Youth Court Law and §§ 20 and 21 Penal Law. The verification of FASD, however, is often difficult, as illustrated by a case report. © 2017, Springer-Verlag GmbH Deutschland.