Ok... so its not an ''invention'' as such but it would work. They already have machines that show what a persons aura is showing at any moment in time so using them as 'Lie detectors' isn't that far fetched.
Aura Imaging - AuraCam 6000 / Coggins Camera
“There is no harder misfortune in all human history than when the powerful of the earth are not also the first men. Then everything becomes false and awry and monstrous. And when they are even the last men and more beast than man, then the value of rabble rises higher and higher and at last the rabble-virtue says: Behold, I alone am virtue.”- S.A.Israel