The libellee, in support of his objection to the testimony which was admitted to prove adultery on several other occasions, since the date of the libel, out of the limits of the Commonwealth, relies upon the case of Commonwealth v. Horton, 2 Gray, 354. It was there held, upon the trial of an indictment for adultery with a person named, that evidence of subsequent cohabitation in another county was not admissible. This decision was by a majority of the court. It is put upon the familiar principle in criminal law, that evidence tending to prove a similar, but distinct offence, for the purpose of raising an inference or presumption that the accused committed the particular act with which he is charged, is not admissible. The case cited was followed by Commonwealth v. Thrasher, 11 Gray, 450, where it is broadly laid down that acts of improper familiarity, amounting to adultery, between the same parties, before the time relied on as the time of the commission of the adultery charged, is inadmissible, either in corroboration of the witnesses for the Commonwealth, or to show the disposition of the parties to commit the crime. Both these cases follow and approve Commonwealth v. Merriam, 14 Pick. 518, where it was held that other instances of improper familiarity between the defendant and the same woman might be given in evidence to corroborate the witness; but both reject such evidence where it tends to show a substantial act of adultery on a different occasion.
If these two cases are to be regarded as stating the true rule . *113which governs the admission of this kind of evidence, then the defendant’s objection is well taken. In the opinion of the court, there is in each case a plain misapplication of the rules of evidence to the facts presented.
The evidence by which the act of adultery is proved is seldom direct. The natural secrecy of the act makes it ordinarily impossible to prove it, except by circumstantial evidence. The circumstances must be such, indeed, as “to lead the guarded discretion of a reasonable and just man to the conclusion of guilt.” But when adulterous disposition is shown to exist between the parties at the time of the alleged act, then mere opportunity, with comparatively slight circumstances showing guilt, will be sufficient to justify the inference that criminal intercourse has actually taken place. The intent and disposition of the parties towards each other must give character to their relations, and can only be ascertained, as all moral qualities are, from the acts and declarations of the parties. It is true, that the fact to be proved is the existence of a criminal disposition at the time of the act charged; but the indications by which it is proved may extend, and ordinarily do extend, over a period of time both anterior and subsequent to it. The rules which govern human conduct, and which are known to common observation and experience, are to be applied in these cases, as in all other investigations of fact.
An adulterous disposition existing in two persons towards each other is commonly of gradual development; it must have some duration, and does not suddenly subside. When once shown to exist, a strong inference arises that it has had and will have continuance, the duration and extent of which may be usually measured by the power which it exercises over the conduct of the parties. It is this character of permanency which justifies the inference of its existence, at any particular point of time, from facts illustrating the preceding or subsequent relations of the parties. The rule is, that a condition once proved is presumed to have been produced by causes operating in the usual way, and to have continuance till the contrary be shown.
The limit, practically, to the evidence under consideration is *114that it must be sufficiently significant in character, and sufficiently near in point of time, to have a tendency “to lead the guarded discretion of a reasonable and just man ” to a belief in the existence of this important element in the fact to be proved. If too remote or insignificant, it will be rejected, in the discretion of the judge who tries the case. The fact that the conduct relied on has occurred since the filing of the libel does not exclude it; and proof of the continuance of the same questionable relations during the intervening time, as in the case at bar, will add to its weight.
It is noticeable, that, while both of the cases first named are placed upon the same rule of evidence in criminal proceedings, they both recognize the principles here stated, and also the exception to the rule, which permits the proof of a distinct offence, when such evidence, tends to establish an element in the crime charged, as when guilty knowledge or some particular criminal intent is to be shown. But by the application of the rule laid down in these cases, evidence tending to establish an independent crime is to be rejected, although all acts which are only acts of improper familiarity are to be admitted in proof. There is no sound distinction to be thus drawn. There is no difference between acts of familiarity and actual adultery committed, when offered for the purpose indicated, except in the additional weight and significance of the latter fact. The concurrent adulterous disposition of the defendant and the particeps criminis cannot be shown by stronger evidence than the criminal act itself. There is no one act by which the moral status of the parties is more clearly defined. And for the purposes and with the limitations here stated, evidence of it is always admissible. Boody v. Boody, 30 L. J. (N. S.) Prob. & Adm. 23. Commonwealth v. Lahey, 14 Gray, 91. Commonwealth v. Pierce, 11 Gray, 447.
Decree affirmed.