We think there was error in refusing to give the fourth instruction, on the ground that the defendant *723could not show title out of the plaintiff without connecting himself with such outstanding title. This is a correct principle of law, hut is applicable only where the defendant seeks to attack a title under which both himself and the plaintiff claim. Love v. Gates, 3 D. & B., 363; Gilliam v. Bird, 8 Ired., 280; Christenbury v. King, 85 N. C., 230; Ryan v. Martin, 91 N. C., 464.
It is true that in our case both parties claim under Kil-lian, but the defendant, under the instruction asked; does not propose to impeach Killian’s title, but contends that, although the plaintiff may have derived title from him, it has been divested by sale under execution, and, therefore, he is not entitled to recover.
In ejectment the plaintiff must recover upon the strength of his own title, and it is always competent for the defendant to show title out of him, where this can be done without encountering the rule of practice commonly called estoppel. Clegg v. Fields, 7 Jones, 37. Even had the defendant entered as the tena'nt of the plaintiff, he could have shown that the title of the latter had- been divested by a sale under execution, and thus have resisted a recovery. Lancashire v. Mason, 75 N. C., 455. A fortiori, can this be done where no such relation exists.
It is urged, however, that the error is harmless, because there appears to have been no testimony identifying the land in question with that described in the Sheriff’s deed. The case states that the defendant offered no such testimony, but as it does not purport to set out the evidence in full, and as the ruling of his Honor .seems to assume the existence of such testimony (possibly disclosed by the plaintiff’s witnesses), we do not feel warranted in saying that the error was not prejudicial to the defendant; and especially is this so, when the point does not seem to have been made upon the trial below. It is further contended that the plaintiff’s deed is void because of the insanity of the plaintiff when the judg*724ment was rendered, and at the time of the sale under execution.
The authorities seem to be in entire accord in holding that such a judgment is voidable only. 1 Black on Judgments, 205; Freeman on Judgments, 142; Freeman on Executions, 22. See also Wood v. Watson, 107 N. C., 52.
It is also well settled that “whatever irregularity there may be in a judgment, if it be an act of a Court of competent jurisdiction, unreversed and in force when a sale is made by execution under it, the purchaser at such saléis safe, even though the judgment be subsequently reversed or set aside. The same principle applies to an -error in the execution, the regularity of which cannot be questioned in an action against a purchaser at a Sheriff’s sale.” See cases in Battle’s Digest, 559; 6th Digest, 264, and 7th Digest, 279.
It is true that where the plaintiff in the judgment is the purchaser, the sale may be set aside on the ground of irregularity, but unless this is done the title passes, and cannot be attacked collaterally. Benners v. Rhinehart, 107 N. C , 705. For these reasons, we .think, there should be a new trial.
Error.