delivered the opinion of the Court.
The points presented in this case, are brought before this court, by the motion for a new trial, filed in the court below by the plaintiff in error. The first that is considered material to determine, relates to the sustaining of the demurrer to the plea of set-off, interposed by the plaintiff. The plaintiff, upon filing his plea of set-off, sent out a notice to the defendant, to apprize him of the fact that he intended to introduce, upon the -trial, evidence to establish his demands as set up in his plea. The court, upon the motion of the defendant in error, struck out the notice for the want of the signature of the plaintiff; and this is assigned for error. "We do not conceive it necessary to investigate this *100ground of objection, since it is in no way legitimately involved. A set-off may be given in evidence under tbe general issue, or pleaded in bar. But when it is intended to be insisted on in evidence, notice shall be given, at tbe time of pleading the general issue, of the demand so intended to be insisted upon, and upon what account the same became due. See Dig., p. 938, sec. 4. The plaintiff has not confined himself to his notice, but pleaded specially his plea of set-off; and, consequently, if that plea, were good with a legal notice, it would be equally so without it. The question then recurs as to the sufficiency of the plea, considered without reference to the notice. If two or more persons are mutually indebted to each other by judgments, bonds, bills, notes, bargains, promises, accounts, or the like, and one of them commence an action against the other, one debt may be set-off against the other, although such debt may be of a different nature. See Dig., 937, sec. 1. There can be no doubt but that tJie matter set up in the plea, is such as may be offered by waj? of set-off, it being an actual subsisting indebtedness, and not a mere possibility and sounding in damages, which are wholly unliquidated. But there exists more doubt in relation to the form of the plea interposed in the present instance. The law requires much strictness in pleas of this nature, as they constitute a sort of new case brought for the first time by the defendant against the plaintiff; and, consequently, the party pleading takes upon himself all the responsibilities of one who, for the first time, puts the law in motion. Tie not only undertakes to defend against a claim preferred against him by the plaintiff, but he also attempts to thwart him in his recovery ; and, in some instances, to recover against him by producing an entirely new case, and one that has no connection with the one sought to be enforced against him.
In point of form the plea of set off should not only contain all the requisites essential to the validity of other pleas in bar, but must describe the debt intended to be set-off, with the same certainty as in a declaration for the like demand. See Chit. plead., vol. 1, p. 562. The plea under consideration, simply avers that *101the plaintiff was indebted to him, the defendant, in the sum of seventy four dollars and eighty cents, at, and before the commencement of the suit, but is utterly silent as to whether it was due and owing or not, at the time of the plea pleaded. It most unquestionably would not suffice for a declaration simply to allege an indebtedness, at a time prior to the institution of the suit, aud to remain silent as to the existence of that fact at that period. Pleading the plea of set-off is the first presentation of the claim of the defendant against the plaintiff, and if not due and owing at the time it is introduced, in contemplation of law it is utterly unfounded; and, consequently, affords no defence against the action. The demands set up by way of set-off, may have been due and owing from the plaintiff to the defendant at the time of the institution of the suit, and yet the last cent may have been paid and discharged before the filing of the plea. Indeed, this is the legal presumption, as he has failed to charge otherwise in his plea; it being a rule of law that the construction is to be taken most strongly against the party pleading, upon the supposition that he has made the most favorable case for himself that the circumstances would permit. We think it clear, therefore, that the plea was demurrable for this reason; and that, consequently, the Circuit Court committed no error in sustaining tlio demurrer to it. It is also contended, that the court below erred in permitting the defendant in error to read a paper, purporting to be a bill of particulars, and a judgment of a justice of the peace, founded upon it, rendered in favor of the plaintiff and against the defendant. This was manifestly error, for there was no issue between the parties, under which the evidence could have been admissible. The plea of set-off under which the plaintiff proposed to introduce the bill of particulars, as appears from his notice, had been swept from under him by the demurrer; and, consequently, the defendant had no legal presumptions to rebut by introducing the judgment.
The next enquiry is, as to the competency of the witness, Me-Knight, to testify in behalf of the defendant. The objection was made at the trial, and overruled by the court. Where the inter*102est is of a doubtful nature, tbe objection goes to tbe credit and not to the competency of tbe witness. A party has such a direct and immediate interest in tbe event of a cause as will disqualify him, when tbe necessary legal consequence of a verdict will be to better bis situation by either securing an advantage or repelling a loss: be must either be gainer- or loser, by tbe event. A witness is also interested, if tbe record would be tbe instrument of securing to him some advantage, or of repelling some charge against him, or claim upon him, in a future proceeding. See Stark. Ev., vol. 2, p. 747-8. The witness stated, upon bis voir dire, that be first went to tbe defendant’s to assist Mace in tbe business of brick-making, under an agreement with Mace, and for no certain wages; that be worked under that agreement about two weeks, when be and Mace changed it, so that he (witness) instead of wages for time, was to have tbe half of the amount to be paid from Robinson for tbe making of the brick. Here is an interest, that is direct and certain, and the record of the judgment, if for Mace, would most clearly have been an instrument by which an-advantage would have been secured to the witness, líe was to have the one-half tbe amount which Robinson should pay, and tbe object of introducing bis testimony, was to fix and determine that amount: Tbe court, therefore, erred in permitting him to testily in tbe cause.
We now come to consider of tbe last objection, which we conceive to be material, and that relates to tbe instruction of the court in reference to the question of skill and diligence. It appears, from the testimony of McKnight, that Mace, the defendant in error, bossed the job, and bad charge of it as a brick-mason. It is questionable whether tbe term “brick-mason, ” is sufficiently comprehensive, properly and technically speaking, to embrace brick makers and brick burners: yet it is obvious, from the expression used, and the other evidence in the cause, that the defendant hold himself out to the plaintiff as a man fully competent to make and burn brick; and, if so, the law is well settled that he will be held to skill and diligence in the execution of his undertaking. This *103being the case, it follows, as a necessary consequence, that if he did not use such skill and diligence as were necessary to make the brick, and to set and burn them in a proper and workmanlike manner, he was guilty of a breach of the contract, on his part, and that he could be held liable in a cross action for damages commensurate with the injury thus sustained by the plaintiff. JBut lie has not seen fit, on this occasion, to resort to his cross action; but, on the contrary, has introduced his proof, and claims, as a defence to the present action, that he has a right to recoup the damages which he may be entitled to for a breach of the stipulations on the part of the defendant. This he most clearly had a right to do. The damages claimed for a failure to exercise proper skill and diligence in the making and burning of the brick, are not sought to be recovered by way of set-off, but by way of recoupment. Recoupment differs from set-off, in two essential particulars: that is to say, in being confined to matters only arising out of and connected with the contract, upon which the suit is brought, and in having no regard to whether or not such matters be liquidated or unliquidated. See 7 Eng. R. 703; Wheaton, use &. vs. Dotson.
We entertain no doubt of the right of plaintiff in error to recoup any damages which he may have sustained, by reason of a breach of the contract concerning the making and burning of the bricks in question; and that, consequently, the court erred in otherwise instructing the jury. In respect to the propriety of striking out the notice for want of the signature of the plaintiff' in error, or of his attorney, we will merely remark, that that was a matter of practice, and within the sound discretion of the Circuit Court, and as there is nothing indicating an unwarrantable or arbitrary exercise of that discretion, it cannot be regarded as error.
The bill of exceptions in this case, has been very inartificially framed, and has given the court much trouble and extreme labor, to ascertain the true position of the parties, and to apply legal principles to the facts therein presented. We are of opinion that error has intervened in the court below, and that the cause ought *104to be, and is hereby reversed, and remanded to be proceeded in, according to law, and not inconsistent with this opinion, and that both parties have leave to amend their pleadings, if they shall desire to do so.
Before Mr. Justice "Walkek, and Hon. Tiiojias JohNSON, Special Judge.
Mr. Oh. Justice ENGlish not sitting in this cause.