Mycology is the study of fungi of all kinds, including blights, moulds, mildews, mushrooms, plant and human pathogens, lichens, rusts and smuts, slime-moulds, truffles, and yeasts. The use of mycological evidence in criminal investigations, and its testing in the courts, i.e. forensic mycology, has until recent years largely been restricted to cases involving poisonous and psychotropic species. However, during the last 3 years we have found various situations in which fungal data can provide critical evidence. The objectives of this review are both critically to consider the published information, and to draw attention to the range of situations where we now know mycological data can be informative – including our personal experience in criminal cases. Applications include roles in: providing trace evidence; estimating time since death (post-mortem interval); ascertaining time of deposition; investigating cause of death, hallucinations, or poisonings; locating buried corpses; and biological warfare.