What Is Evidence?
Mr. Stephen, in his able Treatise on the Criminal Law of England, gives the follow definitions of Evidence:
All the facts with which we are acquainted, visible or invisible, internal or external, are connected together in a vast series of sequences which we call cause and effect; and the constitution of things is such, that men are able to infer from one fact the existence, either past or future, of other facts. For instance, we infer from a footmark on soft ground that a foot has been impressed upon it. From the fact that a man is planting his foot on soft ground, we infer that if he completes that motion a footmark will appear. Any specific fact, or set of facts, employed for the purpose of inferring therefrom the existence of any other fact, is said to be evidence of the fact. Suppose the question is whether John Smith is living or dead: A says, “I knew John Smith, and I saw him die.” B says, “I knew John Smith. I saw him in bed; he looked very ill. I shortly afterwards heard he was dead, and saw a funeral procession, which I attended, and which every one said was his funeral, leave his house and go to the churchyard, where I saw a coffin buried with his name on it.” C says, “Z told me that he heard from X that John Smith was dead.” D says, “I had a dream that John Smith was dead.” Each of these facts, if used for the purpose of supporting the inference that John Smith was really dead, would be evidence of his death. The assertions of A and B would, under ordinary circumstances, be convincing; that of C far from satisfactory, and that of D altogether idle, except to a very superstitious person. This would be usually expressed by saying that the assertions of A and B would be good evidence, that of C weak evidence, and that of D no evidence at all of the fact of the death. But this is not quite a correct way of speaking; whether one fact is evidence of another, depends on the way in which it is used. If people usually believed in dreams, the assertion that a man had dreamt of John Smith’s death would be evidence of his death. Whether or not it would be wise to allow it to be evidence of his death, would depend on the further question, whether in point of fact the practice of inferring the truth of the dream from the fact of its occurrence, usually produced true belief.
It would, unquestionably, aid the ends of justice if the real nature of evidence were better understood; which can only be assisted by the right use of reason.