SeaJayPea:
'Section 20' = GBH.
Emmalu:
As SeaJayPea indicates, the key question is whether or not the US authorities regard your offence as constituting 'moral turpitude'. If not, given the length of time that has passed, a visa application would probably be accepted, with only a short processing time.
However if it's regarded as 'moral turpitude' then, in the first instance, the US Embassy MUST refuse to issue a visa. (It's written into the US Immigration & Nationality Act). They can then refer your request to Washington as an application for a 'waiver of permanent ineligibility'. While you might well get such a waiver, the processing time is many months. (The longest wait I've seen reported here on AB was from someone who had 2 convictions for driving without insurance. His application took 15 months to process, and was then refused).
Chris