There seems a lot of confusion on this point. If you have committed a crime (or even been arrested and not charged), the US embassy will say you must get a visa.
However, under the Visa Waiver Programme, all you have to do is tick a yes/no box ...
'Have you ever been arrested or convicted for an offense or crime involving moral turpitude or a violation related to a controlled substance; or been arrested or convicted for two of more offenses for which the aggregate sentence to confinement was five years or more; or been a controlled substance trafficker; or are you seeking entry to engage in criminal or immoral activity?
I've been into the US many times, seven times this past year, and I have routinely entered on the Visa Waiver Programme. I have an old charge from the early 90's for DUI in the US, and am routinely questioned on this, but still let in.
This week I have been at the US embassy applying for a visa, and was told that any crime against the person, property or the government is 'moral turpitude'. i.e. for DWI I can not use the VWP, and must get a visa.
However today I have come across the US Dept of State Foreign Affairs Manual, chapter 9 re: visas (the 'horses mouth').
It lists what and is not moral turpitude. It is impossible to summarise law, but it seems to require some malicious (or even 'evil') antisocial intent to harm others.
So there would seem to be a lot of minor crimes that are not covered under 'moral turpitude', and it would seem that a lot of people who have committed minor crimes can travel to the US on the VWP and honestly tick the above mentioned box 'no'.
http://foia.state.gov/masterdocs/09fam/0940021 aN.pdf The embassy requirements, and that of the VWP seem contradictory. If anyone considers this an incorrect conclusion I'd be