Answer:
guilty knowledge test
Step-by-step explanation:
Guilty knowledge test: The guilty knowledge test is also denoted as GKT, and is referred to as the psycho-physiological questioning technique which is being utilized as a part of the polygraph examination that assesses the suspects in terms of concealing guilty knowledge through measuring his or her physiological response while performing a specific series of a few multiple-choice questions.
The given statement in the question signifies that the investigators were using the guilty knowledge test.