my son was arrested for breaking and entering

Having a lawyer present is always helpful. However, the arraignment is merely a formal reading of the charges and the setting of bond. Raising the question of criminal responsibility is a matter best left to an attorney. Both your son's mental ability to understand the charges against him, as well as the nature of the proceedings, the role of the court, prosecutor and witnesses, as well as his ability to understand and assist in his defense are matters that need to be addressed, separately from his criminal responsibility. Unfortunately some courts will not address criminal responsibility  in felony cases until the matter has been bound over to the circuit court. But none the less the  issue does need to be preserved, and his competency to stand trial addressed as soon as possible.