The Modern Tendency Regarding the Competency of a Witness to Testify

The modern tendency regarding the competency of a witness to testify, where that witness has been judged mentally incompetent or insane, is:

A) the fact that the witness has been found on previous occasions to be mentally incompetent disqualifies that witness from testifying.
B) testimony of a person who has been found mentally incompetent is inadmissible unless he or she has been adjudicated sane before the trial begins.
C) an adjudication of insanity and confinement in a mental hospital renders the testimony of the witness incompetent.
D) not a bar to serving as a witness so long as the mentally defective person meets the four elements of competency required of other witnesses, generally.