BACKGROUND: Gas gangrene is a clostridium infection primarily of muscle tissue, most commonly caused by C. perfringens. Clinical diagnosis is usually made by local inspection of the wound: the infected tissue shows characteristic signs of tissue inflammation with blistered changes. The disease can starts suddenly, 4-6 hours after the injury, but most commonly the incubation period lasts 2-4 days. Without proper medical intervention, death occurs in 4-24 hours after the development of the first symptoms, but even with timely and adequate therapy, the lethality is very high (around 12%). Due to its fulminant course, in all cases with fatal outcomes, a forensic autopsy is an obligatory procedure. However, discovering the entrance gate and source of infection is not an easy task, especially in the absence of a traumatic injury. CASE PRESENTATION: Male, 27 years old, an intravenous heroin addict for about 10 years, injured his left leg in a traffic accident. He only visited the doctor after 5 days. Upon examination, it was determined that there were no externally visible injuries and no fracture, and he was given a splint immobilization for an ankle luxation. Twelve days after the accident (or 7 days after the immobilization) his mother found him unconscious. CONCLUSION: From medicolegal aspects, it’s important to have in mind even the less frequent paths of infection, in order to give an expert professional opinion on origin and cause of death.