Congenital cranial vascular foramina may mimic fractures on imaging, potentially leading to errors in forensic injury severity assessment. This article reports the case of a 42-year-old male who sustained a blunt force head trauma. Multiple computed tomography scans initially revealed a linear hypodense shadow in the left temporal bone, diagnosed as a skull fracture and subsequently assessed as Minor Injury Grade II. Upon forensic re-evaluation, a longitudinal comparison with pre-injury imaging was conducted. Detailed analysis utilizing three-dimensional reconstruction technology demonstrated that the radiological finding was present prior to the injury. Furthermore, post-injury follow-up scans showed no morphological change or callus formation, characteristics consistent with a congenital vascular foramen rather than an acute fracture. Consequently, the injury severity was revised to Slight Injury. This case underscores the critical importance in forensic clinical practice of obtaining detailed medical history, systematically reviewing pre-injury imaging, and employing advanced image post-processing techniques for differential diagnosis. Such an approach helps prevent misdiagnosis due to anatomical variants, ensuring the objectivity and accuracy of injury severity assessment and upholding judicial integrity.