Maiestas
in Roman criminal law, meant the inviolable dignity or sovereignty of the State; and all conduct derogatory to the dignity or power of the people, or of those to whom the people had intrusted power, was crimen imminutae maiestatis (De Invent. ii. 17, 53). This particular conception of treason appeared late in the history of the Republic, and was at first supplementary to the older conception of perduellio. An attack upon the existence of the State was perduellio; anything less than this was the crime of impaired majesty. The Republican laws de maiestate were all passed in a period of bitter, and often bloody, political strife, and all the prosecutions under these laws were essentially partisan. The expression imminuta maiestas seems first to have been used in the lex Apuleia (B.C. 103?); and the principal object of this law, apparently, was to protect the sovereignty of the people as incorporated in the tribunate. The conception was further developed by a lex Varia (B.C. 90?) and (in the conservative interest) by a lex Cornelia of Sulla (B.C. 80), until the crime against majesty practically covered and included perduellio. In a lex Iulia (ascribed by some authorities to Julius Caesar, by others to Augustus, while others again hold that there were two leges Iuliae de maiestate), the two crimes were fused, and perduellio thenceforward meant simply a grave case of lese-majesty (cf. Inst. 3, 1, 5; Dig. 48, 4, 11; Codex, 9, 50, 2). This lex Iulia remained the basis of the law of treason through the Imperial period, but the number of possible offences against majesty was greatly increased by succeeding statutes. The maiestas publica was primarily and chiefly embodied in the person of the emperor (maiestas principatus, augusta); and the crimen laesae maiestatis included not only acts injurious to the State, but all plots against the emperor and his family, and all acts derogatory to his dignity and honour. Thus libels upon the emperor, destruction of his statues, false or violated oaths per genium principis, and, under some of the more tyrannic rulers, hostile and even disrespectful speech were punished as lesemajesty. Arcadius, who repealed all laws of the last-mentioned character, extended the law of treason to include plots against the higher officials of the Empire (A.D. 397).Trials for perduellio, under the Republic, were always in comitiis—i. e. prosecution took the form of a bill, and the decision lay with the popular assembly. Prosecutions de maiestate, on the other hand, were conducted before special courts (quaestiones). In the early Imperial period cases of treason were tried by the Senate; later by the emperor himself or his praefects. Accusation could be brought, even under the Republic, by slaves, infamous persons, and others who were debarred in ordinary criminal cases; and under the emperors torture was applied to freemen and even to persons of rank (honorati) for the purpose of obtaining evidence.
The penalty in the Republican period was exile, or rather outlawry (aquae et ignis interdictio). In the Empire it varied, according to the gravity of the offence, the social position of the offender, and the temper of the reigning emperor, from death in various forms (humiliores vestiis obiiciuntur vel vivi exuruntur, honestiores capite puniuntur, Paul, v. 29, 1) to scourging or simple relegatio. In both periods the extreme penalty carried with it the escheat or confiscation of the criminal's property, and, under the Empire, attainder of the blood, so that the sons of the criminal could neither hold office nor take inheritances or legacies (Codex, 9, 8, 5). The same results attached to condemnation when prosecution was instituted after the death of the criminal (damnatio memoriae). See Zumpt, Das Criminalrecht der röm. Republik (1868), ii. 1, 226-237, 249- 258, 376-392; and Rein, Das Criminalrecht der Römer (1844), 506-597.