The US Immigration and Nationality Act places a lifetime bar on anyone entering the USA who has been convicted of an offence of moral turpitude (except when they were a minor at the time of the offence, and there was only a single offence). So the US Embassy staff have no discretion when it comes to considering visa applications from such people; they must (in every case) refuse the application.
However US law also provides that the Department of Homeland Security may issue a 'waiver of permanent ineligibility'. If such a a waiver is granted, the Embassy may then reconsider the application.
So the first stage of seeking the relevant 'waiver' is always to submit a new visa application (together with the relevant police documentation) and to attend the interview. At that stage a request for the application to be referred to Washington (and to be treated as a 'waiver' application) can be made. (However it might possibly accelerate matters if a letter is sent with the visa application, stating that the applicant is seeking a 'waiver of permanent ineligibility').
The total processing time is a MINIMUM of 5 months, but can frequently be MUCH longer. Someone posted, here on AB, to say that her husband had waited for 15 MONTHS before having his waiver application turned down (for two offences of driving without insurance). So (given that there's no point in booking travel before finding out whether a visa will be issued) it's already getting late to apply for travel in 2013.
The USA doesn't recognise the UK's Rehabilitation of Offenders Act (and has no equivalent legislation), so there are no rules about when (if ever) an offence may be disregarded for immigration purposes; every application is processed individually. However I've seen it suggested that a MINIMUM 10-year period is applied to those offences which might eventually be disregarded. So your brother probably has some sort of chance of being admitted (but it's still also possible that he'll never be allowed to enter the USA). The only way to find out is to apply a.s.a.p.
Chris



