“First, as regards the finger-prints of which so much has been heard and so few have been seen.
“Every one is satisfied that the murderer wore gloves, because nowhere else in the study, where he must have handled one thing after another, were any finger-prints found. They are found, these important pieces of evidence, upon the one object where their presence is utterly damning—and there only!
“The spirals, whorls, and what-nots which compose these marks correspond exactly with those to be found in the skin and thumb and first two fingers of Archibald Deacon’s right hand. Ergo, say Police and Public, Archibald Deacon is the murderer. But I say that these finger-prints go a long way to prove (even without the rest of my evidence) that Deacon cannot be the murderer.
“Here is the one really clever murder (of those discovered) committed within the last fifteen years. Yet, if one take the popular view, one has to believe that the murderer, who was wise enough to wear gloves during the greater part of the time he was in the study, actually removed one of them and carefully pressed his thumb and fingers upon the highly receptive surface of his weapon’s handle before leaving that weapon in a nice easy place for the first policemen to find!
“Surely the fallacy of blindly accepting as the murderer the man who made those prints is obvious? Consider the position of the marks. They point down the handle, towards the blade! It is almost incredible that at any time would the murderer have held the weapon as a Regency buck dandled his tasselled cane.
“My difficulty was to reconcile with Deacon’s innocence of the murder the presence of his finger-prints upon the tool with which it was committed. That the prints were his I had too much respect for the efficacy of the Scotland Yard system to doubt.
“A possible solution came to me from memory of a detective story[²] I once read, in which the murderer, something of a practical scientist, made, by means of an ingenious and practicable photographical process, a die of another’s man’s thumb-print. This he used to incriminate the innocent owner of the thumb.
“For a while I cherished this theory, so vivid was my recollection of the possibility of the method; but I was never really satisfied. Then, suddenly, I found the explanation which I was afterwards to prove true.
“Instead of going to the immense trouble of making a stamp or die, why not obtain beforehand upon the desired object the actual finger-prints of the chosen scapegoat?
“After consideration, I accepted this idea. It fitted well enough with my murderer—a fellow of infinite cunning. I proceeded with the work of reconstruction. Thus:—