Q. "How do you know?"
A. "He always locks the door."
Witness after witness will take the stand and testify positively that certain events took place, or certain acts were done, when in point of fact all they can really swear to is that they usually took place or usually were done:
Q. "Did he put on his hat?"
A. "Certainly he did."
Q. "Did you see him?"
A. "No, but he must have put on his hat if he went out."
And the probability is that the whole question to be determined was whether or not "he" did go out or stay in.
The layman chancing to listen to a criminal trial finds himself gasping with astonishment at the deluge of minute facts which pour from the witnesses' mouths in regard to the happenings of some particular day a year or so before. He knows that it is humanly impossible actually to remember any such facts, even had they occurred the day before yesterday. He may ask himself what he did that very morning and be unable to give any satisfactory reply. And yet the jury believe this testimony, and because the witness swears to it it goes upon the record as evidence of actual knowledge. In ninety-nine cases out of a hundred counsel's only recourse is to argue to the jury that such a memory is impossible. But in the same proportion of cases the jury will take the oath of the witness against the lawyer's reasoning and their own common-sense. This is because of the fictitious value given to the witness's oath by talesmen who attach little significance to their own. "He swears to it," says the juryman, rubbing his forehead. "Well, he must remember it or he wouldn't swear to it!" And the witness probably thinks he does remember it.