1. The evidence that the person assaulted was, at the time of the assault, and with the defendant’s knowledge, acting as a police officer, and wearing the uniform and badge of such an officer, was competent and sufficient evidence of his official capacity to be submitted to the jury. The want of similar proof as to any other time might affect the weight, but not the competency, of this evidence. Commonwealth v. Kane, ante, 423. Sawyer v. Steele, 3 Wash. C. C. 464. Plumer v. Brisco, 11 Q. B. 46. Regina v. Vickery, 12 Q. B. 478. Regina v. Murphy, 8 C. & P. 297, 310.
2. A constable has the right, by virtue of his office, and without any warrant, to enter any house, the door of which is unfastened, and in which there is a noise amounting to a breach of the peace, and to arrest any person engaged in an affray or in committing an assault in his presence, and hold him by suitable means for a reasonable time to prevent any further assault; and an assault by such a person upon the officer so arresting and holding him is an assault upon an officer in the discharge of his duty. Commonwealth v. Hastings, 9 Met. 259. Any affray or assault is a disturbance of the peace, and might properly be so called by the officer in answering the defendant’s inquiry as to the cause of his arrest. The final instruction given to the jury was therefore correct and sufficient.
3. The subsequent failure of the officer to make a complaint before a magistrate against his prisoner for the offence for which he had arrested him — whatever effect it might have to render the officer hable to an action of trespass by the latter—cannot affect the question whether his assault upon the officer was a breach of the criminal law. This question depended upon the facts and circumstances existing at the time when the assault was made. One ground of the doctrine of trespass ah initia, which, for reasons of public policy and the protection of the citizen against oppression, will not allow one, who abuses an authority given him by the law, to shelter himself under such authority when sued by the person injured by the abuse, is, that the citizen is bound to submit without resistance to its lawful exercise. Esty v. Wilmot, 15 Gray, 168,169. The doctrine of trespass ab *430initia has no application to criminal cases. The degree of a crime, once completed, cannot be aggravated by the subsequent act of the criminal, or lessened by that of a third person. In State v. Moore, 12 N. H. 42, it was held that a person who had lawfully entered a house could not be made a burglar by afterwards stealing therein. The subsequent act or omission of the officer, not part of the same transaction, nor immediately connected in point of time with his arrest of his prisoner or the assault upon him by the latter, was not admissible in evidence against the Commonwealth in a prosecution for that assault. The offence of the defendant was complete as soon as he had assaulted the officer lawfully holding him, and might have been immediately made the subject of an indictment. The subsequent failure of the officer to do a distinct act, which the law required him to do in the further discharge of his duty, could no more affect the degree of the defendant’s previous offence than it could the question of probable cause for such a prosecution. Wilder v. Holden, 24 Pick. 8. Williams v. Babbitt, 14 Gray, 141, 142. If the officer had no authority to discharge his prisoner from custody without bringing him before a magistrate, he certainly had no greater authority to release him from his responsibility to the Commonwealth for the offence already committed. It was therefore rightly ruled that the failure of the officer to complain against and prosecute the defendant for that offence could not avail him in this case.
It would seem, from the bill of exceptions, that the only cause for the arrest of the defendant, upon which the Commonwealth relied at the trial, or was allowed by the court to sustain the indictment, was a disturbance or breach of the peace. But if the defendant, at the time of assaulting the officer, was under arrest because he had been found in a state of intoxication committing a breach of the peace, the result must have been the same. By the St. of 1869, o. 415, § 42, if any person “is found in any place in a state of intoxication committing a breach of the peace, or disturbing others by noise,” any constable or police officer ‘ shall without a warrant take him into custody, and detain him in some proper place until, in the opinion of such officer, he is so far recovered from his intoxication as to render it proper to carry *431him before a court of justice ; ” and “ the officer shall then take him before some justice of the peace or police court in the city or town where he has been found, and shall make a complaint against him for the crime of drunkenness.” If the defendant was arrested by the officer as directed by the first clause of this section, his assault upon the officer while thus lawfully under arrest was not rendered less criminal by the subsequent failure cf the officer to comply with the second clause of the statute.
Exceptions overruled.