Recently I came across one of television’s true crime programs that presented a provocative example from actual case files: A woman had been brutally murdered in her apartment. Her former boyfriend with whom she had recently had a vigorous altercation became the leading murder suspect. During the investigation, this man was “offered” a polygraph (lie detector) test in the attempt to establish his likely guilt or innocence. He agreed to be tested and was found to have “failed,” thus presumably indicating his likely guilt.
Despite this result, the evidence presented at the trial was deemed insufficient for a guilty verdict, and he was acquitted. Convinced that the polygraph test was accurate, his local community made him a pariah; he was shunned and even threatened with bodily harm. Several months later, however, another man, the actual murderer, was apprehended and convicted. Thus at least for this first suspect, despite his ordeal, the story had a satisfactory ending, and the lie detector test itself proved inaccurate and misleading. This outcome leads to an obvious question: How often does “lie detection by machine” prove false?