To extrapolate on what Tim W has said: the act of murder generally requires the presence of intent. It's not necessarily the case that the intent must be to actually kill someone - because the intent can be to 'grievously harm' them (each state is different in their requirements, this is the Queensland example). When I say 'generally' there's also the incidence of unlawfully killing someone while being recklessly indifferent to human life but this is predicated on the accused being aware of the probability (not just possibility) of the act resulting in a person's death.
If someone is found to be 'insane' then that means they cannot form the necessary intent required for the act to be murder; or even to be aware of the probability that the act would result in death.
While you can be correct in saying he was accused of murder (and should probably add that he was found not guilty due to lack of capacity, or what the actual finding was), you cannot say that he is a murderer. He hasn't been found guilty of murder. You or anyone else can't make the determination that he is. Doing so is the sole reserve of the courts and they found differently.
If someone is found to be 'insane' then that means they cannot form the necessary intent required for the act to be murder; or even to be aware of the probability that the act would result in death.
While you can be correct in saying he was accused of murder (and should probably add that he was found not guilty due to lack of capacity, or what the actual finding was), you cannot say that he is a murderer. He hasn't been found guilty of murder. You or anyone else can't make the determination that he is. Doing so is the sole reserve of the courts and they found differently.