Petechial hemorrhages are ruptures of the (microscopic) capillaries that provide blood to the body’s cells. Oxygenated blood travels from the heart through vessels (called arteries) of sequentially smaller and smaller size until they become the smallest vessels, called capillaries. Blood eventually returns to the heart through sequentially larger and larger vessels (called veins) in order to be reoxygenated. If the veins in an area of the body are obstructed or compressed, blood flow back to the heart from beyond such a point can be impeded. In these circumstances, blood will still flow through the arteries, but it will be (fully or partially) prevented from flowing back to the heart through the veins. Rather, blood will collect more distal to the compression, for example in a leg, arm or the head. This may result in a spike in blood pressure in that area, which, in turn, causes the rupture of the capillaries. These ruptures cause petechial hemorrhages. One possible cause of such petechial hemorrhages is a compression of the neck sufficient to compress the veins, but insufficient either to compress the arteries or cause a cardiac arrest. Such a crush could result in blood continuing to flow into, but not out of, the head, causing the aforementioned backing up of blood in the head. However, this is not the exclusive cause of petechial hemorrhages, and I do not believe that such was the cause of this decedent’s petechial hemorrhages. For instance, other possible causes of petechial hemorrhages are vomiting and severe coughing, which can also compress veins through muscular contraction.
Petechial hemorrhages medical expert witness specialties include forensic pathology.