Stab wounds are commonly encountered in forensic pathology practice and part of their examination and interpretation involves wound-depth measurements, which may provide information about the possible length of the implement. It is suggested that different body positions during life, such as leaning forward or standing up, may cause the internal organs to move relative to each other, and thus the stab wound depth in a non-supine position might be different when measured supine at post mortem examination. Whether internal organs move relatively in different post mortem positions is not well documented yet. This study documented significant post mortem anterior displacement of the heart when the body is prone compared to being supine, up to 32.7 mm. The displacement correlated negatively to weight and body mass index in certain locations, but not with age or height. This study provides evidence that when measuring a stab wound at post mortem examination, the position of the body can be a significant confounding factor affecting the accuracy of measurement and may have significant forensic relevance.