A petechial hemorrhage is a tiny pinpoint red mark that is an important sign of asphyxia caused by some external means of obstructing the airways. They are sometimes also called petechiae. Their presence often indicates a death by manual strangulation, hanging, or smothering. The hemorrhages occur when blood leaks from the tiny capillaries in the eyes, which can rupture due to increased pressure on the veins in the head when the airways are obstructed. If petechial hemorrhages and facial congestion are present, it is a strong indication of asphyxia by strangulation as the cause of death .
The forensic pathologist usually needs a very good light source and maybe even a magnifying glass to detect petechial hemorrhages. They range in size from the size of a speck of dust to around two millimeters and may occur in distinct groups. Often they are seen in the conjunctiva of the eyes and also on the eyelids, especially after hanging. They may also be found elsewhere on the skin of the head and face, such as in the mucous membrane inside the lips and around or behind the ears. When found in a case of suspect hanging, the presence of petechial hemorrhages strongly suggests the victim was hung when still alive. This helps distinguish hangings staged to make a murder look like a suicidal act.
Petechial hemorrhages on the face are also found in other conditions such as cardiac arrest. Internal examination may reveal petechiae on the surfaces of the lungs and heart in cases of death by heat stroke and sudden infant death syndrome (SIDS, or crib death). In the latter circumstances, they are not considered a cause of the child having been smothered or otherwise asphyxiated. The forensic pathologist will also look out for petechiae in cases of sexual assault. Petechial hemorrhage may also occur postmortem as the capillaries start to break down, but these lesions tend to be rather bigger than pinpoint size and may blur into one another rather than occurring as distinct groups. As ever, the pathologist must be aware of all the circumstances surrounding the death when interpreting these findings.
see also Asphyxiation (signs of); Hanging (signs of).