Supervised Release & Violations
Almost every federal offense carries with it a term of supervised release. Supervised release is like "probation:" a defendant must report to the Probation Office, submit to drug testing and abide by the law and standard conditions of supervised release.
There are, unfortunately, many ways to violate supervise release - not submitting monthly reports, having a dirty drug test, or being arrested for new criminal conduct. The best thing a defendant can do in those situations is to immediately call his or her public defender. Often, defense counsel can work with their client and with Probation to avoid supervised release violations being charged.
When a Probation Officer files supervised release charges, they are contained in a charging document called a "Petition." If the defendant cannot afford an attorney, the public defender will be appointed for these revocation proceedings.
The defendant has much more limited rights in revocation proceedings than when facing substantive federal charges. For example, at a revocation hearing there is no jury. The government need only prove the charges by a preponderance, instead of beyond a reasonable doubt. Also, hearsay is admissible, so a Probation Officer can simply repeat the allegations of other witnesses in the hearing.
In reality, there are very few full revocation proceedings. Most frequently, a deal is worked out that requires an admission of some of the charges, and an agreed-upon sentence.
While the defendant has a right to a full sentencing memo from Probation, in many cases the parties simply agree to move directly to sentencing on the day the charges are admitted. The judge does not have to follow the recommendations of the party, but typically does defer to any agreement that arrived upon by the parties and Probation.