Finding out whether a crime is one of moral turpitude is a sticky topic, as the goal posts are constantly moving with new cases appearing in the states.
Best bet is to look at the district of columbia codes - as this is what foreign convictions are compared against, and see what fits for what you have been charged with.
Relate that to previous examples of crimes involving morale turpitude. Examples can be found www.state.gov/documents/organization/86942.pdf
Take all your documents with you when you go, including PNC record, and district of columbia code.
As I take it you were finderprinted, your details are now on the PNC and subdequently on the NCIC, which links the US-VISIT, so the US will know.
If you are found not guilty, and this is the only time you have been arrested, immediately write to the chief constable and ask for your details to be removed from the PNC. You are legally entitled to do this - Google "removing records from pnc" for more information. Chief Constables WILL fight this request, but the law is on your side.