delivered the opinion of the Court:
The first assignment of error relates to the refusal of the court to direct a verdict for the plaintiff. Marriage has been said to be the most important relation in life, and that it has more to do with the morals and civilization of the people than any other institution. “The consent of the parties is of course essential to its existence, but when the contract to marry is executed by the marriage, a relation between the parties is created which they cannot change. Other contracts xnay be modified, restricted, or enlarged, or entirely released upon the consent of the parties. Not so with marriage. The relation once formed, the law steps in and holds the parties to various obligations and liabilities. It is an institution in the maintenance of which in its purity the public is deeply interested, for it is the foundation of the family and of society, without which there would be neither civilization nor progress.” Maynard v. Hill, 125 U. S. 190, 211, 31 L. ed. 654, 659, 8 Sup. Ct. Rep. 723. Again, in Andrews v. Andrews, 188 U. S. 14, 30. 47 L. ed. 366, 368, 23 Sup. Ct. Rep. 237, the court referred to marriage as “'interwoven with the very fabric of society.” It has come to pass, therefore, that courts frown upon all agreements between husband and wife having for their object the procurement of a divorce. Good faith is demanded of the parties to a divorce proceeding, to the end that the court may be fully advised as to the facts. And any agreement between such parties made with an intent to promote or facilitate the procurement of a divorce tends to close avenues of information and mislead the court. Sheehan v. Sheehan, 77 N. J. Eq. 411, 140 Am. St. Rep. 566, 77 Atl. 1063; Pereira v. Pereira, 156 Cal. 1, 23 L.R.A.(N.S.) 880, 134 Am. St. Rep. 107, 103 Pac. 488; Birch v. Anthony, 109 Ga. 349, 77 Am. St. Rep. 379, 34 S. E. 561; Stokes v. Anderson, 118 Ind. 533, 4 L.R.A. 313, 21 N. E. 331; Wolkovisky v. Rapaport, 216 Mass. 48, 102 N. E. 910, Ann. Cas. 1915A, 809; Pierce v. Cobb, 161 N. C. 300, 44 L.R.A.(N.S.) 379, 77 S. E. 350, 9 R. C. L. 254.
*350However, it.is- no longer open to question that where a separation'actually has occurred, or is to occur immediately, a deed of separation between the parties will be upheld; and “this is especially true if the separation was 'occasioned by the misconduct of the husband, and the provision for the wife’s support was reasonable under the circumstances, and no more than a court before which she was entitled to carry her grievances would have decreed to her as alimony.” Walker v. Walker (Walker v. Beal) 9 Wall. 743, 751, 19 L. ed. 814, 818; Winter v. Winter, 191 N. Y. 462, 16 L.R.A.(N.S.) 710, 84 N. E. 382. And such a deed of separation is no bar to the bona fide application by either party for divorce. J. G. v. H. G. 33 Md. 401, 3 Am. Rep. 183; Clark v. Fosdick, 118 N. Y. 7, 6 L.R.A. 132, 16 Am. St. Rep. 733, 22 N. E. 1111, 23 N. E. 136; Archbell v. Archbell, 158 N. C. 408, 74 S. E. 327, Ann. Cas. 1913D, 261.
But in the present case, there is evidence tending to show that the execution of this contract by the defendant may have been induced by a promise on the part of the plaintiff that she would procure a divorce from him; in other words, that this contract, although valid on its face, disclosed only a part of the agree.ment, and that the real agreement contemplated a severance of the marriage ties in such a way that the court would be led to believe that the parties really were adversary'and that all the facts were before the court, when in truth there was no real defendant, the interest of each party being to make a case warranting a decree. If such an agreement existed, it was collusive, and amounted to a fraud upon the court.
It is insisted, however, that in the circumstances of this case the defendant ought not to be permitted to plead his own turpitude. It is pointed out that the divorce was granted, is still in force, that the defendant has married on the strength of it,, and now is seeking to avoid obligations which the law would have imposed upon him. But the difficulty is, irrespective of our opinion of his conduct, we must look beyond the parties, and if satisfied that the public interest will best be 'subserved by a refusal to aid in the enforcement of this contract, we must take notice of the facts, from whatever source they come. That *351the public ini crest is involved already has been made to appear. “The court refuses to enforce such a contract, and it permits defendant to set up its illegality, not out of any regard for the defendant who sets it up, but only on account of the public interest. It has been often stated in similar cases that the defense is a very dishonest one, and it lies ill in the mouth of the defendant to allege it, and it is only allowed for public considerations and in order the better to secure the public against dishonest transactions.” McMullen v. Hoffman, 174 U. S. 639, 669, 43 L. ed. 1117, 1128, 19 Sup. Ct. Rep. 839. The evidence being conflicting’ upon this branch of the case, there was a question for the jury.
The plaintiff requested the court to charge the jury that the “burden of proof rested upon the defendant to establish by a preponderance of evidence that the plaintiff promised in consideration of his making the agreement that she would procure a decree of divorce.” This request was denied, and over the objection and exception of the plaintiff the court instructed the jury, as requested by the defendant, “that the burden of proof is upon the plaintiff to prove by a preponderance of the evidence that there was no understanding between the plaintiff and defendant that plaintiff would procure the divorce from the defendant in consideration of the defendant’s entering into the agreement in suit.” The action of the court in refusing the instruction requested by the plaintiff and in granting that submitted by the defendant is assigned as error.
The admission of the execution of the contract by defendant amounted to a waiver of the plea of non est factum. See 1 Chitty, Pl. 16th Am. ed. 629; 2 Chitty, Pl. 401: State use of Herdman v. Houston, 1 Harr. (Del.) 230; Union Bank v. Ridgley, 1 Harr. & G. 324. There remained, therefore, the pleas setting up the special matter of defense. The contract being complete in itself and expressing a valuable consideration (Walker v. Walker (Walker v. Beal) 9 Wall. 743, 19 L. ed. 814; Winter v. Winter, 191 N. Y. 462, 16 L.R.A.(N.S.) 710, 84 N. E. 382), proof of it and the breach assigned made a case for the plaintiff. The defendant, however, by liis pleas alleged facts tending to avoid the contract, and he introduced evidence *352tending to support those averments. In other words, he in effect admitted that the contract on its face was valid, but that an additional undisclosed consideration rendered the contract illegal, and hence relieved him from all obligation thereunder. There was no issue as to the contract as written and proved: Had there been, the burden would have been on the plaintiff. Tinker v. Midland Valley Mercantile Co. 231 U. S. 681, 683, 58 L. ed. 434, 435, 34 Sup. Ct. Rep. 252. Under the facts stated, the issue was narrowed to the question whether there was an understanding between plaintiff and defendant that the plaintiff would procure a divorce from the defendant in consideration of the defendant’s entering into the agreement. The , defendant having tendered this issue, the burden was upon him to establish it. Thus, in McMullen v. Hoffman, 174 U. S. 657, 43 L. ed. 1124, 19 Sup. Ct. Rep. 839, the court says that the “burden of proof is on the obligor to show the real consideration;” and again, on page 658, after a review of the authorities, the court says: “These authorities uphold the principle that tire whole case may be shown, and the plaintiff cannot prevent it by proving only so much as might sustain his cause of action, and then objecting that the defendant himself brings in the balance, which it was not necessary for plaintiff to prove.” As further authority for the proposition, see also Ripy v. Art Wall Paper Mills, 41 Okla. 20, 51 L.R.A.(N.S.) 33, 136 Pac. 1080; Bibb v. Allen, 149 U. S. 481, 37 L. ed. 819, 13 Sup. Ct. Rep. 950; McBratney v. Chandler, 22 Kan. 692, 31 Am. Rep. 213; Couch v. Hutchinson, 2 Ala. App. 444, 57 So. 75; Anderson v. Carlson, 99 Ill. App. 514. It is apparent, therefore, that the jury should have been instructed that the defendant had assumed and should carry the burden of this issue, which, as we have seen, became the only issue in the case. Of course, where there are several issues, the ultimate burden is upon the plaintiff to establish his case. Sullivan v. Capital Traction Co. 34 App. D. C. 358. In Central Vermont R. Co. v. White, 238 U. S. 507, 512, 59 L. ed. 1433, 1436, 35 Sup. Ct. Rep. 865, Ann. Cas. 1916B, 252, 9 N. C. C. A. 265, it was stated “that the United States courts have uniformly held that as a matter of general law the burden of proving contributory negligence is on the defend*353ant,” but by that expression the court did not intend to intimate that on the whole case the burden was not upon the plaintiff.
The judgment must be reversed, with costs, and the cause remanded for further proceedings. Reversed and remanded.