“Bear with me, sir.  The science of evidence being thus so extremely subtle, and demanding the most acute and trained observation of facts, the most comprehensive understanding of human psychology, is naturally given over to professors who have not the remotest idea that ’things are not what they seem,’ and that everything is other than it appears; to professors, most of whom by their year-long devotion to the shop-counter or the desk, have acquired an intimate acquaintance with all the infinite shades and complexities of things and human nature.  When twelve of these professors are put in a box, it is called a jury.  When one of these professors is put in a box by himself, he is called a witness.  The retailing of evidence—­the observation of the facts—­is given over to people who go through their lives without eyes; the appreciation of evidence—­the judging of these facts—­is surrendered to people who may possibly be adepts in weighing out pounds of sugar.  Apart from their sheer inability to fulfil either function—­to observe, or to judge—­their observation and their judgment alike are vitiated by all sorts of irrelevant prejudices.”

“You are attacking trial by jury.”

“Not necessarily.  I am prepared to accept that scientifically, on the ground that, as there are, as a rule, only two alternatives, the balance of probability is slightly in favour of the true decision being come to.  Then, in cases where experts like myself have got up the evidence, the jury can be made to see through trained eyes.”

The Home Secretary tapped impatiently with his foot.

“I can’t listen to abstract theorising,” he said.  “Have you any fresh concrete evidence?”

“Sir, everything depends on our getting down to the root of the matter.  What percentage of average evidence should you think is thorough, plain, simple, unvarnished fact, ’the truth, the whole truth, and nothing but the truth’?”

“Fifty?” said the Minister, humouring him a little.

“Not five.  I say nothing of lapses of memory, of inborn defects of observational power—­though the suspiciously precise recollection of dates and events possessed by ordinary witnesses in important trials taking place years after the occurrences involved, is one of the most amazing things in the curiosities of modern jurisprudence.  I defy you, sir, to tell me what you had for dinner last Monday, or what exactly you were saying and doing at five o’clock last Tuesday afternoon.  Nobody whose life does not run in mechanical grooves can do anything of the sort; unless, of course, the facts have been very impressive.  But this by the way.  The great obstacle to veracious observation is the element of prepossession in all vision.  Has it ever struck you, sir, that we never see any one more than once, if that?  The first time we meet a man we may possibly see him as he is; the second time our vision is coloured and modified by the memory of the first.  Do our friends