The Guilty Knowledge Technique is a method that involves the detection of knowledge about a crime as a means for inferring deception. It has been promoted as an alternative or replacement for the commonly used Control- Question Technique in investigative polygraph examinations; however, guilty-knowledge tests have rarely been used in actual investigations, and some authors have suggested that practical considerations prevent their widespread use. The current study found that guilty-knowledge tests might have been used in 13.1 percent of the examinations (95 percent confidence interval for similarly selected examinations: 4.9 percent to 21.4 percent). A large proportion of the remaining examinations were conducted under circumstances that would not be amenable to the use of guilty-knowledge tests, even with much effort. The results, although not fully conclusive for reasons that are discussed, indicate that the Guilty Knowledge Technique might be applied in a small proportion of FBI cases, but there is no basis to consider it as a general replacement for current methods. Recent reports of novel physiological parameters and methods of analysis for use with guilty-knowledge tests may be of limited value in criminal investigations. 35 references