"Absence of proof is not proof of absence" [ attributed to William Cowper 1731-1800]

Society of Expert Witnesses Conference on "Immunity and Uncertainty" Studely Castle Warwickshire on Friday October  6th 2006

by Dr Antony Anderson CEng FIEE

The recent widespread  introduction of automobile electronic control systems - for example, electronic throttle control, anti-lock braking and automatic stability systems - has fundamentally altered the relationship between driver and vehicle. The  driver  now controls the vehicle indirectly by means of a number of surrogate electronic control systems, which may exhibit a will of their own and a capability to respond unpredictably and sometimes dangerously. A system designed to control speed may malfunction and cause a loss of speed control. A system designed to improve vehicle stability may cause the vehicle to become unstable. Intermittent electronic system malfunctions often caused by electromagnetic interference or software glitches - are notoriously difficult to diagnose because, unlike hardware faults, they leave little trace behind them afterwards. Switch a malfunctioning electronic system off and on again and it resets and behaves normally for days, weeks, months or even years. Attempts to reproduce the failure mode are often fruitless. However, failure to diagnose or reproduce the malfunction does not mean that the malfunction never occurred, in other words:  "Absence of proof is not proof of absence". In fact the only proof of the incident may lie in the characteristics of the event itself. Unfortunately, in the courts absence of proof may well be accepted as proof of absence: i.e. if no physical evidence can be found of an electronic malfunction then there can have been no electronic malfunction: ergo it must have been the driver who was at fault.  Antony Anderson uses examples from his electrical and electronic casework to illustrate how "Absence of proof is not proof of absence". Hopefully he will stimulate discussion on how to minimize the risk of drivers unjustly carrying the can for the occasional, but inevitable, intermittent malfunctions of safety-critical automobile electronic control systems.

Return to Section 6 : Frequency of sudden unintended acceleration incidents and alleged examples