First, in court, the best state of theory is to achieve a tripartite balance between prosecution, defense and trial.
Especially the current sentencing can also be debated in court. For example, the procuratorial organs put forward sentencing suggestions, defense lawyers put forward defense opinions, and the two sides debated, which virtually restricted the judge's discretion. This is to tell you that the judge can't judge whatever you want! Ensure that there is no arbitrary power of any party and strengthen supervision and checks and balances on judicial power!
Second, if the defendant is a professional lawyer, there is absolutely no need to hire a lawyer.
Most citizens can't have professional legal knowledge and necessary defense skills, which is why the defendant needs to hire a lawyer to defend him. In the debate between the prosecution and the defense, the lawyer only speaks for the defendant. Of course, the defendant has the right to speak, and it's too powerful. This right of defense is originally the defendant's. In fact, the defendant can completely stop the lawyer from speaking and defend himself.
Of course, when debating, there is an order in the court. You don't have to say it if you want, but you must get permission from the court.