how do you assess for compentecy to stand trial?

Answer 1

Psychological Assessment of Competency to Stand Trial
In Criminal Court, competency comes into question in several different areas of legal proceedings. First, a defendant has to be competent to waive Miranda rights, if a confession is to be used at trial. The defendant has to be competent to stand trial, and if convicted, competent to be sentenced and competent to serve a sentence. Of course, the individual must also be found to have been competent at the time of the offense, in order to have criminal responsibility for the crime. Further, in cases where the death penalty is a possible consequence, the person must be found competent to be executed.

The confusing issue in these competency determinations, is that one determination of competency does not automatically lead to other findings of similar competency. In other words, a person can be competent at the time an offense is committed, but later not competent to stand trial. If the person was not competent at the time of the offense (criminal responsibility for the act), that does not mean that he/she is not competent later to stand trial. The term temporary insanity has been used to explain this defense, although that term is not used in New Jersey law. Further, if a person is not currently competent to stand trial, the trial can be delayed until he/she is competent to stand trial. However, the court will eventually dismiss the charges, if there is no indication that competency will not return later, following treatment.

Answer 2

It's done by a psychologist (PhD) or psychiatrist (MD). The usual standard is does the defendant understand the charge, and can he/she assist in the defense against the charge.