If you have already told them you did not take the money, stop talking to the police now. Polygraphs are not what you think - they are an interrogation tool and rarely benefit the defendant. Stop talking to the police, stop thinking about a polygraph, and if you think you are going to be charged, retain a defense lawyer in your area.
There is no statutory right to a speedy trial in South Carolina. Two years may violate the Constitutional right to a speedy trial, but you will not usually win on this argument at the trial level in a magistrate or municipal court. Time is your friend in a DUI case, and if there are no problems other than the length of time it has been pending, you should trust that your attorney knows what he or she is doing.
Were you wrongfully convicted or wrongfully charged but not yet convicted? If you have already been convicted you have 10 days to file notice of appeal or up to one year to file an action for post conviction relief. Either way you need an attorney to help with this - you cannot be charged or convicted of DUI on a moped, assuming it is under 50cc's, but people get charged, there are prosecutors who will go forward on the charge, and there are magistrates who will allow it to stand.
DUAC is not a reduced charge, and it has the same consequences as a DUI. Neither DUI nor DUAC can be expunged after three years. Although most magistrate court offenses can be expunged after three years, this does not apply to driving offenses.
If this is a DUI 1st offense, your son needs to request a jury trial before his initial court date, and he needs to request an administrative hearing within 30 days.
If you can afford to retain a private attorney you should, but I would not...
Tell him not to make any statements, do not talk to police or the former employer, and to talk with an attorney as soon as possible. It will be better if arrangements can be made through an attorney to have the warrant served on him.
Only if he was sentenced under the Youthful Offender Act (YOA) and he has no other convictions since. If he was convicted since and is serving time on a federal charge, he cannot get it expunged even if it was a YOA sentence. His only option is to apply for a pardon, and he would want to wait some time after the federal sentence is finished before applying.
Your case is still pending and your license is still suspended. To begin with, you need to request a jury trial before the court date on your ticket, and you need to request an administrative hearing within 30 days of your arrest to get your license back. As soon as you request the administrative hearing you can get a temporary license to drive on until after the hearing. Get an attorney to help you with this.
Get an attorney and request a jury trial. It may be dismissed or it may be a case that can be tried. If not, it may be possible to do a conditional discharge or pre-trial intervention. All of the above can keep it off of her record.