That branch of jurisprudence which treats of crimes and offences. From the very nature of the social com- pact on which all muncipal law is founded, and in consequence of which every man, when he enters into society, gives up part of his natural liberty, result those laws which, in certain cases, authorize the in- fliction of penalties, the privation of liberty, and even the destruction of life, with a view to the future prevention of crime and to insuring the safety and well-being of the public. Salus populi suprema lex. The extreme importance of a knowledge of the criminal law is evident. For a mis- take in point of law, which every person of discretion not only may know but is bound and presumed to know, is in criminal cases no defence. Ignorantia eorum quæ quis scire tenetur non excusat. This law is ad- ministered upon the principle that every one must be taken conclusively to know it without proof that he does know it; per Tindal, C. J., in 10 Cl. & F. 210. See 11 Blatchf. 200:59 Ala. 57; 65 Me. 30; 39 N. J. L. 402. And this is true though the statute making an act illegal is of so recent pro- mulgation as to make it impossible to know of its existence; 8 Ala: 119; 8 Ga. 380; 1 Gall. C. C. 62. This doctrine has been carried so far as to include the case of a foreigner charged with a crime which was no offence in his own country; 1 E. & Β. 1; Dearsl. 51; 7 C. & P. 456; Russ. & R. 4. See 50 Ind. 341. And, further, the crimi- nal law, whether common or statute, is im- perative with reference to the conduct of individuals; so that, if a statute forbids or commands a thing to be done, all acts or omissions contrary to the prohibition or command of the statute are offences at common law, and ordinarily indictable as such; Hawk. Pl. Cr. bk. 2. c. 25, § 4; 8Q. B. 883. See 15 M. & W. 404. An offence which may be the subject of criminal pro- cedure is an act committed or omitted in violation of a public law either forbidding or commanding it; 144 U. S. 677. In seeking for the sources of our law up- on this subject, when a statute punishes a crime by its legal designation, without enumerating the acts which constitute it, then it is necessary to resort to the common law for a definition of the crime with its distinctions and qualifications. So if an act is made criminal, but no mode of prose- cution is directed or no punishment pro- vided, the common law furnishes its aid, prescribing the mode of prosecution by in- dictment, and as a mode of punishment, fine, and imprisonment. This is generally designated the common law of England; but it might now be properly called the com- mon law of this country. It was adopted by general consent when our ancestors first settled here. So far, therefore, as the rules and principles of the common law are ap- plicable to the administration of criminal law and have not been altered and modified by legislative enactments or judicial deci- sions, they have the same force and effect as laws formally enacted; 5 Cush. 303, 304; 4 Metc. Mass. 358; 13 id. 69, 70. "The common law of crimes," says an able writer, "is at present that jus vagum et incognitum against which jurists and vindi- cators of freedom have strenuously protest- ed. It is to be observed that the defini- tions of crimes, the nature of punishments, and the forms of criminal procedure origi- nated, for the most part, in the principles of the most ancient common law, but that most of the unwritten rules touching crimes have been modified by statutes which as sume the common-law terms and defini- tions as if their import were familiar to the community. The common law of crimes has, partly from humane and partly from corrupt motives, been pre-eminently the sport of judicial constructions. In theory, indeed, it was made for the state of things that prevailed in this island and the kind of people that inhabited it in the reign of Richard I.; in reality, it is the patchwork of every judge in every reign, from Cœur de Lion to Victoria." Ruins of Time Ex- emplified in Hale's Pleas of the Crown, by Amos, Pref. x. Some of the leading principles of the English and American system of criminal law are-First. Every man is presumed to be innocent until the contrary is shown; and if there is any reasonable doubt of his guilt, he is entitled to the benefit of the doubt. See 123 U. S. 623. Second. In general, no person can be brought to trial until a grand jury on examination of the charge has found reason to hold him for trial. 121 U. S. 1. Third. The prisoner is entitled to trial by a jury of his peers, who are chosen from the body of the people with a view to im- partiality, and whose decision on questions of fact is final. Fourth. The question of his guilt is to be determined without reference to his general character. By the systems of continental Europe, on the contrary, the tribunal not only examines the evidence relating to the offence, but looks at the prob- abilities arising from the prisoner's pre- vious history and habits of li