INCOMPATIBILITY. offices, rights. This term is used to show that two or more things ought not to exist at the same time in the same person; for example, a man cannot at the same time be landlord and tenant of the same land; heir and devise of the same thing; trustee and cestui que trust of the same property.

2. There are offices which are incompatible with each other by constitutional provision; the vice-president of tho United States cannot act as such when filling the office of president; Const. art. 1, s. 3, n. 5; and by the same instrument, art . 1, s. 6, n. 2, it is directed that "no senator or representative shall, during the time for which he was elected, be appointed to any civil office under the authority of the United States, which shall have been created or the emoluments whereof shall have been increased, during such time; and no person holding any office under the United States, shall be a member of either house, during his continuance in office."

3. Provisions rendering offices incompatible are to be found in most of the, constitutions of the states, and in some of their laws. In Pennsylvania, the acts of the 12th of February, 1802, 3 Smith's Laws of Pa. 485; and 6th of March, 1812, 5 Sm. L. Pa. 309, contain various provisions, making certain offices incompatible, with each other. At common law, offices subordinate and interfering with each other have been considered incompatible; for example, a man cannot be at once a judge and prothonotary or clerk of the same court. 4 Inst. 100. Vide 4 S. & R. 277; 17 S. & R. 219; and the article Office.

INCOMPETENCY, French law. The state of a judge who cannot take cognizance of a dispute brought before him; it implies a want of jurisdiction.

2. Incompetency is material, ratione materia, or personal, ratione personae. The first takes place when a judge takes cognizance of a matter over which another judge has the sole jurisdiction, and this cannot be cured by the appearance or agreement of the parties.

3. The second is, when the matter in dispute is within the jurisdiction of the judge, but the parties in the case are not; in which case they make the judge competent, unless they make their objection before they. take defence. See Peck, 374; 17 John. 13; 12 Conn. 88; 3 Cowen, Rep. 724; 1 Penn. 195; 4 Yeates, 446. When a party has a privilege which exempts him from the jurisdiction, he may waive the privilege. 4 McCord, 79; Wright, 484; 4 Mass. 593; Pet. C. C. R. 489; 5 Cranch, 288; 1 Pet. R. 449; 4 W. C. C. R. 84; 8 Wheat. 699; Merl. R«p. mot Incompet«nce.

4. It is a maxim in the common law, aliquis non debet esse judex in propriŠ causa. Co. Litt. 141, a; see 14 Vin. Abr. 573; 4 Com. Dig. 6. The greatest delicacy, is constantly observed on the part of judges, so that they never act when there could be the possibility of doubt whether they could be free from bias, and even a distant degree of relationship has induced a judge to decline interfering. 1 Knapp's Rep. 376. The slightest degree of pecuniary interest is considered as an insuperable objection. But at common law, interest forms the only ground for challenging a judge. It is not a ground of challenge that he has given his opinion before. 4 Bin. 349; 2 Bin. 454. See 4 Mod. 226; Comb. 218; Hard. 44; Hob. 87; 2 Binn. R. 454; 13 Mass. R. 340; 5 Mass. R. 92; 6 Pick. 109; Peck, R. 374; Coxe, Rep. 190; 3 Ham. R. 289; 17 John. Rep. 133; 12 Conn. R. 88; 1 Penning R. 185; 4 Yeates, R. 466; 3 Cowen, R. 725; Salk. 396; Bac. Ab. Courts, B; and the articles Competency; Credibility; Interest; Judge; Witness.