In reading a few other posts, it appears some are confusing competency with NGRI. These are two different things. Criminal charges involve two prongs. Actus Reus (
guilty act,
link) and Mens Rea (
guilty mind,
link). NGRI, also known as the M'Naughten rule (
link), applies to the "
mens rea" of the defendant, and is a defense that can be put forth at trial. NGRIs are rarely used as a defense ( < 1%) due to public disfavor. Competency, otoh, has to do with whether (
or not) the defendant can make sound legal decisions. And since the legal process, in and of itself, is quite complex, it can involve several competency hearings:
Competency to waive Miranda Rights
Competency to stand trial
Competency to be sentenced
Competency to waive appeals (arguably, for each possible appeal)
Competency to be executed
So, for example, in competency to stand trial, does the individual understand the charges? Can they assist in their defense? In competency to waive appeals, does the individual understand the consequences of waiving the appeal, etc. In all cases but Miranda, if the individual is found to be incompetent, they are remanded to a mental institute to be restored to competency. The latter, specifically, competency to be executed, raises several ethical Qs, and was extensively discussed in the case of Singleton v Norris. (
link)