Abstract Legal difficulties can always arise when a death, owing to a pre-existing natural disease, follows trauma. Arteriovenous malformations of the brain are well known to rupture spontaneously, causing severe and often fatal cerebral haemorrhage. When such rupture is preceded by head injury, it is necessary to consider whether the rupture was coincidental or a direct result of the physical injury sustained. The standard of evidence required for criminal conviction in such cases must be ‘beyond any reasonable doubt’. The present article discusses the relationship between physical trauma and cerebral arteriovenous malformation in an adult male who died following an altereation with a colleague that resulted in his being punched in the face, falling down and hitting his head.