Although polygraph examinations continue to be used widely
concerns are growing about the errors made by examiners.
To study this issue, researchers obtained the actual polygraph records
of 50 criminal suspects who were later found to be innocent
and 50 suspects who later confessed to their crimes (all suspects had been accused of theft).
The researchers asked six expert polygraph examiners to decide
which suspects appeared to be guilty on the basis of the polygraph record.
How well did the polygraph experts do at detecting lies?
Overall, the polygraph experts correctly categorized about two-thirds of the suspects
(76% of the guilty individuals and 63% of the innocent), as shown by the solid bars on the graph.
The experts made two types of errors:
Misses, in which they failed to identify 24% of the guilty suspects
and False Alarms, in which they incorrectly accused 37% of the innocent people of lying.