Blow back phenomenon seen in

Blow back phenomenon in hard contact: This is most frequently seen in gunshot wounds on the head where the hot expanding gases forced back between the scalp and skull are released by creating tears in the scalp. The margins will be eveed due to gases coming out under pressure. Sometimes, due to negative pressure tissue fragments may be drawn into the barrel and outside called black spatter. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 148