True, but I used the threat of fingerprint evidence many times to get confessions, often when there could not have possible been any.
Hee-hee! We actually had one gang-banger convinced that a Garrett weapons detector was a lie detector! He was arrogant, cocky and waived his rights under Miranda, so we questioned him about a shooting. He lied out his backside, and we knew it, so one of the guys picked up the Garrett, holding it close enough to his weapon so that it would beep, and at every lie, he would thumb it on...."beep beep"
. The guy confessed to everything & got 15-20 with a gun spec.