Parry, form the US embassy site;
'Under United States visa law people who have been arrested are required to declare the arrest when applying for a visa. If the arrest resulted in a conviction, the individual may be permanently ineligible to receive a visa. In order to travel, a waiver of the permanent ineligibility is required. The Rehabilitation of Offenders Act does not apply to United States visa law. Therefore, even travelers with a spent conviction are required to declare the arrest and/or conviction.
Court records, usually called a "Memorandum of Conviction" (MOC) in Great Britain and Certificates of Conviction in Northern Ireland are obtained from the clerk of the court(s) in which the individual was tried. Such court records must show the nature of the offense(s) committed, the section(s) of law contravened and the actual penalty imposed. If the MOC or Certificate of Conviction is not available from the court in which the individual was tried, he or she can still obtain the court record(s) from a division of New Scotland Yard at the address below, if convicted in the Great Britain, or the Royal Ulster Constabulary station, if convicted in Northern Ireland. In the event that the memorandum of conviction, or Certificate of Conviction is unavailable, the applicant MUST obtain a letter so stating from the Clerk of the Court.
National Identification Service
Subject Access Office
Room 331, New Scotland Yard
Broadway, London SW1 0BG
Tel: 020-7230-2958'
Reading this it appears that if you have a 'conviction' then you should declare it as the Rehabilitation of Offenders Act does not apply to US law, whether or not a 'caution' counts as a conviction is probably something only known to the US Embassy, I think you would be best contacting them to make sure!!
From a bobby who should know probably??
Steve.......................
