¶1It does not appear from the bill of exceptions, what was the consideration, if any, expressed in the bill of sale from Tenable to Jones, and we cannot say whether the court erred or not, in the proof admitted. That such proof is admissible in many cases, see Graham v. Lockhart, 8 Ala. 24.
¶2The objection to the testimony of the witness, Strain, is, that it contradicted the bill of sale made by him to the plaintiff, by which he assumed to sell the slave as his own, and not as the agent of Jones. There can be no doubt, that in an action by the plaintiff against Strain, upon this warranty, he would not be permitted to show that he did not intend to bind himself, but was acting as the agent of another person. But this rule is confined in its operation, to the parties to the written instrument; where it comes in question collaterally, in a suit in which a third person, a stranger to the writing, is a party, neither party is estopped from contradicting it, or from proving facts inconsistent with it. The interest of the witness having been released by the plaintiff, he was a competent witness, and any discrepancy between his testimony and his previous written contract in relation to the same matter, would go to his credit.
¶3Nor do we know of any rule of public policy which would exclude it. He is not swearing here to sustain a title emanating from himself, but to prove that he never had or claimed title to the slave.
¶4Let the judgment be affirmed.