In an effort to lift this thread into the realms of actual discussion:
I seem to be like Russ, an Engineer (by education, anyway) who has been on numerous "ghost hunts", including Craig-Y-Nos, supposedly the most haunted castle in Wales.
Can I prove I was there, that I went on the hunts? Well, if they have kept booking records for the past 10 or so years then perhaps, but otherwise no, no more than you can prove what you were doing 10+ years ago on any given day.
But if you insist on having "proof" that I was there before you'll accept the anecdotal evidence, then we can discount ghosts out of hand from here on out, since there is currently no proof that they exist. No proof, therefore we can dismiss the anecdotal evidence, right?
Anyhoo - now that we've gotten past the nonsense of requesting proof before someone can offer up their anecdotes:
The "tour guides" at each place were the official investigators and seemed quite genuine in their attempts to seek out ghosts, but in our party of ten (at Craig-Y-Nos) there were zero sightings. The unfortunate thing was that every draft, every creak of old floorboards etc, was made out by the investigators to be a possible "paranormal" event.
And this was true in the other locations as well.
The one thing they had in common, however, was that they all try to play on your hypervigilance in dark and often claustrophobic rooms, where the brain starts interpreting what is effectively audio and visual "noise" as being far more than it is in an effort to detect (and thus avoid) threats.
This was the closest any such ghost-hunt could get to having us think we could see/hear things - which was set off when one in the party accidentally stubbed their toe and squealed. The tour-guide was actually intending to document that as a "physical encounter", but my friend in question assured her that she genuinely just missed the step and stubbed her toe.
But while it was all good natured enough, and we weren't there to disrespect their hunting efforts, the disappointing thing to us was that their stock response to the notion that they really just played on the hypervigilance of the tour party was with the "well, you can't prove that it's not ghosts!" type of line.
So there they were trying to prove ghosts exist, and their stock approach was that it would be considered a ghost until proven otherwise. They were hunting with the assumption of existence, yet unwilling/unable to discount more rational explanations for what they discovered.
I.e. they were simply not scientific in their approach, irrespective of how much technical equipment they had. (Using technical equipment does not make the approach scientific!)