someone has asked a similar question a bit lower in this section, and the answer points out that you need a visa if you've ever been arrested, even if you weren't charged, and even if was erased from your record long ago. The theory is that the ever obliging British government will eagerly hand over the records of everyone in the country to the Americans for checking, which wouldn't surprise me. But I don't know how you'd get on in practice if you just flew on the visa waiver programme and omitted to mention your past villainy - has anyone tried this?