Medical and psychiatric aspects of accident investigation.

Biomedical factors account for 80-90% of the 600 aircraft accidents each year. Mechanical failures as causative factors are 10-20%. The biomedical factors of fatalities include use of drugs and alcohol in order to cope with a possible stress, anxiety, or frustration in the aircraft. The important role of personality factors in producing stress reactions requires that stress be defined in terms of transactions between individuals and situations, rather than of either in isolation. When stress reactions are observed, it is assumed that these were brought about by stress conditions, and the accident investigator looks for them in order to understand the reaction which leads to the accident. In the field of fatal accident investigation, where the causes of the event must be sought retrospectively (that is, by looking back and reconstructing the antecedent conditions) the investigator usually assumes that the victim must have encountered severe stress to which the behavior represents a response. Since there are variations in reaction patterns in different individuals under different instances of stress, this issue turns us back to consideration of intervening processes and conditions. An individual's behavior is dependent upon the total effect of all the psychosocial variables that went into the making of this individual's life style.