My SO has a court date for a traffic violation. It shouldn't be that much of a deal except he stutters and it becomes severe when he is under stress. Often he is rendered nearly mute which is why he is having to attend court other than just pay a fine, when asked why he did what he did he was unable to provide an answer. Will I be able to assist him in court? It seems ridiculous to get him an attorney for at most a $500 fine but I don't want him to end up in contempt or getting extremely upset which may not go well.
I think I would type up a note with an outline of the diagnosis and hand it to the clerk of the court.
I don't know if this is true in your jurisdiction, but there is also such a thing as a "next friend" - a person with no professional status but who stands in the participant's corner and lends support. Might be worth asking about.
Anyway - the court's officers are the people to consult, and such people are usually very helpful to ordinary members of the public. It serves justice for everything to be done fairly, after all, and they are servants of the justice system.
In the future, I would have him carry a letter from the doctor in his glove compartment.