This is a forensic medical case study focusing on a case of incomplete motor aphasia following an open severe craniocerebral injury. Gan was injured in a traffic accident, resulting in contusion and laceration of the left frontal lobe and multiple traumatic hemorrhages. After undergoing treatments such as intracranial hematoma removal, craniotomy intracranial decompression, and decompressive craniectomy, Gan exhibited symptoms of incomplete motor aphasia, characterized by an ability to understand others’ speech but difficulty in expressing oneself, with unfluent sentences and only being able to slowly and briefly utter single words or phrases. During the forensic medical examination, a detailed analysis was conducted on Gan’s injury history, injury basis, and past medical history. By combining clinical manifestations, treatment process, and dynamic imaging findings, a comprehensive judgment was made on the disability assessment and its degree between the injury and the incomplete motor aphasia.