It is as simple as if you want to believe something badly enough, you will. The easiest way to know the claimant is full of shit is to challenge them to take their claim to a neutral independent lab and have their findings peer reviewed by people with no horse in the race.
If the claimant reacts with "No" it is a very simple indicator that they are merely protecting their wishes and ego.
If the claimant reacts with "No" it is a very simple indicator that they are merely protecting their wishes and ego.