ASSESSOR. - He is the one who advises and assists the judge in the study and determination of a case. According to the Roman law of the Republic, the intervention of the assessor - also called comes, iuris studiosus, consiliarius - was not at all obligatory and was left each time to the discretion of the judge; later, especially in the imperial provinces, the assessorship became an institution of a permanent character. In canon law, the assessor had the role of a consultant, called, in case of need, to elucidate the points of a particular controversy (c. 11, de rescriptis, I, 3, in VI); and such is he considered also by the Code now in force, which (can. 1575) permits the single judge - and, be it noted, not the collegiate tribunal - to be assisted with consultative vote by no more than two assessors, chosen from among the synodal judges. The assessor takes an oath in accordance with can. 1622 and is bound to official secrecy according to can. 1623.
The first senior official of those three Sacred Congregations (the Holy Office, the Consistorial and for the Eastern Church) which have the Pope as prefect is also called assessor (v. CONGREGAZIONI PONTIFICIE). He is equated in rank, attributions and privileges with the secretaries of the other Congregations (cf. the Constitution Ad incrementum decoris of Pius XI, of 16 Aug. 1934).
In Italian law, the members of the municipal Giunta are called assessors; and this name was also given, from 1931 to 1945, to the five lay judges of the Courts of Assize.