At a Probation Violation hearing, the defendant will get an opportunity to admit or deny the violation. If the defendant denies, a hearing will be scheduled in front of a judge only, and the standard of proof is preponderance of evidence. If the client wants to admit, they need to do waivers of certain rights.
Yes, you would need a certificate to represent someone.
Hope this helps!
First, be sure that you do file a certificate of representation so that you can be heard on the proceeding. Some courts are more stringent about that than others.
Second, yes, if there is reason for withdrawing the plea of guilty and contesting the charge, you should make that motion to the Court as soon as possible, preferably before the probation revocation hearing.
Third, without a successful motion to withdraw the plea of guilty, a probation revocation hearing is likely going to be short-lived. You may get more mileage out of showing for the probation revocation and talking to the Court and prosecutor about the reasons that revocation (or substantial revocation) doesn't make sense in this case and probably should have some material with you (proof of his turn-around). At that point, you are falling on the mercy of the Court.
There is no strict liability in criminal law. He could (with your help or not) request the court reopen the ticket, and put it back on the court calendar. Courts are usually willing to do this. A paid ticket is analogous to a default judgment in a civil case, more or less. A wriiten motion or request may be required.
The court may set it on for an appearance about whether the ticket case should be reopened. Often I have been able to settle the case, on new and improved terms - such as a disposition that would not trigger another license revocation. Also - I try to make sure Court Administration will "de-certify" to MN DPS, the DAR conviction that has been vacated.
The possible probation violation matter may still be a problem, since the burden of proof in those is only "clear and convincing" to a judge. On that I would talk to the probation officer after making sure the client has insurance coverage and a valid license.