¶1Evidence to be competent, must consist of facts of which the witness has personal knowledge. If it be material to show a knowledge by a witness of a particular fact, it may be proper to inquire of him whether the fact was or was not known to him ; of his own mental status he is competent to testify. The mental status, the cognition of another, is not a fact; it is of necessity matter of opinion or conclusion dependent on the facts from which the opinion is formed, or the conclusion drawn. The court below erred in permitting the witness to testify that the defendant knew at the time of the difficulty that Rowell had gone to Loachapoka to get a warrant for him. The facts on which the witness formed the opinion, or from which the conclusion was drawn, should have been stated; the resulting opinion or conclusion was matter lying within the exclusive province of the jury.—P. & M. Bank v. Borland, 5 Ala. 546; Peake v. Stout, 8 Ala. 498; Whetstone v. Bank, 9 Ala. 886; Walker v. Walker, 34 Ala. 473. It is not material that the evidence was drawn out on cross-examination. It is true that when a cross-examination is directed to the credibility of a witness, large latitude *154of interrogation is permissible. But where the evidence is directed to a fact material to the issue, the cross-examination can not be made the medium of introducing illegal or irrelevant evidence ; evidence which would not be received, if the witness had been introduced by the party cross-examing. In Bullock v. Wilson, 5 Port. 338, it was said: “If illegal evidence were allowable on cross-examination, instead of promoting truth, it would rather suppress it; instead of aiding the jury in their deliberations, it would interpose obstacles, instead of enlightening, it would tend to obscure.” We can not know whether the evidence exerted any influence on the minds of the jury or not; that is matter of speculation we are not inclined to indulge ; the presumption of injury to the defendant arises, which we can not say is affirmatively repelled by any matter appearing in the record.
¶2As the judgment must be reversed, we deem it necessary to say in reference to the exclusion of the evidence offered by the defendant, that if his knowledge of the fact of the effort to procure the warrant, or of the fact of its issue was material, it was his right to offer evidence controverting either fact. If the offer included secondary, or illegal evidence, the irregularity can be corrected on another trial.
¶3Reversed and remanded.