2. When a person, charged with a crime, proves (se eadem die fuisse alibi,) that he was, at the time alleged, in a different place from that in which it was committed, he is said to prove an alibi, the effect of which is to lay a founation for the necessary inference, that he could not have committed it. See Bract. fo. 140, lib. 3, cap. 20, De Corona.
3. This proof is usually made out by the testimony of witnesses, but it is presumed it might be made out by writings; as if the party could prove by a record properly authenticated, that on the day or at the time in question, he was in another place.
4. It must be admitted that mere alibi evidence lies under a great and general prejudice, and ought to be heard with un-common caution; but if it appear, to be founded in truth, it is the best negative evidence that can be offered; it is really positive evidence, which in the nature of things necessarily implies a negative; and in many cases it is the only evidence which an innocent man can offer.