Visa waiver / US immigration

This is really aimed at any check in or cabin crew, this is perhaps one of the most regular questions ( and heated arguments between the people who believe that the US has full access to our PNC etc. and the people who say the opposite) that pops up on any US travel forum - regarding criminal records and the visa waiver scheme - so many people must travel under the VWP without the slightest knowledge of whether they need a visa or not - just how often are people denied entry because they have knowingly or unknowingly travelled without a visa, in particular if they have lied and ticked NO on all the questions about arrests/convictions (and been found out somehow)?
I can understand if they have answered YES on the forms - I assume they are on the next plane home?
I would LOVE a definitive answer, one way or the other.

[Darren Wheeler]

Can't help on the specifics, but there is an old saying.....

'Never ask a question to which you don't already know the answer...'

[Nottingham Nick]

I know this topic is banned on the DIBB and is subject to many a heated debate on Flyertalk.com, but is not a subject we touch on very often.

I do not know the answer to how many people are turned away, but and it is a big but; the question on the Waiver form or Have you ever been arrested or convicted for any reason in any country, even if the arrest did not lead to a conviction, or do you have a criminal record? is so sweeping and non-specific, that if you answer 'no' when it isn't true, then you are risking being refused entry.

There are hundreds, if not thousands, of anecdotes by people who have been arrested, cautioned or even convicted then lied and have been admitted, but I would have to ask if it is worth the risk?

I don't think there is a definitive answer because, as we know, 'previous results are not a guide to future performance.' [8D]

Nick