Retrograde blood aspiration: a vital reaction.

Blood aspiration, which is based on an intact breathing activity, is one of the forensically most important vital reactions. On the example of 11 forensic cases it is shown that the aspiration of blood into the lung tissue is possible not only when the bleeding source is situated above the trachea or main bronchi, but also in a retrograde way, taking its origin from an injury of the peripheral lung tissue itself. Equally to 'classical' blood aspiration, the findings of retrograde blood aspiration are to be diagnosed by means of macroscopical and histological examination of the lung tissue. The lung tissue presents with roundish, reddish spots, which are situated close to, but separate from a lung contusion or other lung tissue injury, and microscopical examination reveals blood in the alveoli and the bronchioli. Retrograde blood aspiration may be a helpful vital sign in the forensic assessment of thorax trauma cases where no other vital reactions are present.