The study is intended to aid forensic physicians in assessing the cause of death or the mental competence of persons exposed to tear gas. Although chloroacetophenone has been known to cause deaths when administered in large quantities in a closed room, no deaths have been attributed to chemical mace, probably because it is generally used in small quantities outside. Three degrees of effects from the substance are illustrated with three case studies: 1) little or no effect, with increased aggressivity, 2) normal tearing with abandonment of resistance, and 3) excessive effects characterized by breathing difficulties, fear of suffocation, and a panic reaction. The degree of aggressiveness in the reaction to the substance depends on the individual tolerance to the substance. Death from exposure to mace is shown to be very unlikely. However, death can result from the excitement caused by the mace when severe prior physical damage is present. In evaluating mental competence, the expert may assume that exposure to mace does not produce toxic effects. But indirect effects such as aggressivity, confusion from loss of sight, and panic from fear of suffocation may reduce individuals' ability to function reasonably. A table and a bibliography are supplied.