This paper presents a three-rider motorcycle accident which took place in a suburb of Chongqing China. In the accident, the motorcycle impacted the terminal of a bridge footpath and led to two riders died and one rider injured. After the accident, one rider received injuries around the groin area including the underbelly area and the perineum area. Another rider suffered from injuries only on the perineum areas. In medico-legal judgments, injuries around the groin area also called groin injuries in victims of motorcycle accidents are usually regarded as "fuel tank injuries" which are commonly found in drivers. But, the injuries around the groin area are sometimes confused with the perineum injuries. Therefore, the perineum injuries are often wrongly reckoned as the "fuel tank injuries" and used to identify the drivers too. Actually, passengers can sometimes suffer from perineum injuries in many head-on impacting motorcycle accidents. It is of vital matters to understand the differences between groin injuries and perineum injuries so that the real driver who should be responsible for the accident can be recognized. In this paper, the three-rider motorcycle accident was presented and the injury information of the three riders was studied in order to distinguish the real driver from the riders. We consider that the groin injury has some differences with the perineum injury and the latter should not always be related to the driver especially in high-speed head-on impacting motorcycle accidents. In addition, the injury on underbelly areas is important to identify the driver.