This is a pun on 'sentence' which a set of words that is complete in itself, typically containing a subject and predicate, conveying a statement, question, exclamation, or command, and consisting of a main clause and sometimes one or more subordinate clauses. However, in the context of lawyers/ the court system, 'sentecne' means the punishment assigned to a defendant found guilty by a court, or fixed by law for a particular offense.
If a lawyer speaks for too long there will be an extended sentence .