no they don't, no one takes those tests seriously other than chavs on the jeremy kyle show.
Don't you know that guilty killers have passed lie detectors before then been proven to have been lying?
Lukes tracker dog found the body apparently, yet luke and the dog would have had to have passed the body and the same v break in the wall on the way up the path yet he didnt alert him of anything then? only on the way back down? this is proof it was Luke who found the body and not the dog, and this means Luke wanted to lead the family to the body as he wanted to witness their distress and reaction to his 'work'. truly evil.