Same basic principal as a Lie Detector Test.
Measures body function reaction to certain stimulus.
They should not forget that some people are unaccustomed to having any contact with the law whatsoever, save the rare traffic ticket. These folks are going to be keyed up for the first hour or so.
Conclusion: ‘Mind Reading’ FAIL!
You think the CCP gives a hoot?
If you are evil (and I think we agree the CCP is evil, maybe as evil as democrats) punishing a Innocent harshly produces as valuable an obedience fear based reaction as punishing the guilty.