It sounds like a criminal charge has been filed and that the case/charge is pending. It can be pending investigation. It can be pending at some level within the courts. I am assuming that the facts you have provided go to your belief that he cannot have done what is alleged due to his physical limitations/disabilities. If so, that is a factual assertion which he and his attorney will have an opportunity to present to a jury at some point. His physical condition does not create a legal defense, but only a factual defense. His attorney can explain this in more detail if necessary.
I agree with the first answer. Pending can mean the case has already been started and is pending a final outcome or it can mean that the case is being investigated with a view towards charging the person with a crime. Even if he is charged, his attorney has the chance to present all of the issues you mentioned during the case itself.
I think your answer got cut off in part. Are you saying that a medical condition caused him to fall and the prosecutor's think he deliberately attacked someone?