term:

Incompetent

incompetent adj

1

: not legally qualified: as
a : lacking legal capacity (as because of age or mental deficiency)
b : incapable due to mental or physical condition compare competent
c : lacking authority, power, or qualifications required by law [an court] [ evidence]
2 : unable or failing to perform adequately [fired for being ] [an attorney] compare ineffective assistance of counsel
n : a person who is incompetent compare interdict

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.