Many states have no certification at all. Some are trying. The National Center for State Courts has organized a consortium of states that is sharing resources for establishing standards and testing. Approximately 25 state and local court systems have joined the Consortium. The value of interpreter certification, moreover, depends on the validity of the testing methodology and other certification requirements.
Some states use court interpreter examinations that are of dubious validity.
Federal certification is usually a good indicator of competence. State certification may or may not be a reliable indicator, depending on the state in question. It is a good sign if a translator you are considering is accredited by the American Translators Association in the appropriate language combination. Reliable certification is one of the most important issues of the day. The written examination is slated for November 2001, and the oral is to be administered in February 2002.