“For example, a friend of mine, a professor in a Western university, has carried on experiments with scores of people and has not found one who could give a completely accurate description of what he had seen, even in the direct testimony; while under the influence of questions, particularly if they were at all leading, witnesses all showed extensive inaccuracies in one or more particulars, and that even though they are in a more advantageous position for giving reports than were your clerks who were not prepared.  Indeed, it is often a wonder to me that witnesses of ordinary events who are called upon in court to relate what they saw after a considerable lapse of time are as accurate as they are, considering the questioning they often go through from interested parties, neighbours and friends, and the constant and often biased rehearsing of the event.  The court asks the witness to tell the truth, the whole truth, and nothing but the truth.  How can he?  In fact, I am often surprised that there is such a resemblance between the testimony and the actual facts of the case!

“But I have here a little witness that never lies, and, mindful of the fallibility of ordinary witnesses, I called it in.  It is a new, compact, little motion camera which has just been perfected to do automatically what the big moving-picture making cameras do.”

He touched one of the little black boxes such as we had seen him install in the jewelry department at Trimble’s.

“Each of these holds one hundred and sixty feet of film,” he resumed, “enough to last three minutes, taking, say, sixteen pictures to the foot and running about one foot a second.  You know that less than ten or eleven pictures a second affect the retina as separate, broken pictures.  The use of this compact little motion camera was suggested to me by an ingenious but cumbersome invention recently offered to the police in Paris—­the installation on the clock-towers in various streets of cinematograph apparatus directed by wireless.  The motion camera as a detective has now proved its value.  I have here three films taken at Trimble’s, from different angles, and they clearly show exactly what actually occurred while Mrs. Willoughby and Annie Grayson were looking at the Kimberley Queen.”

He paused as if analysing the steps in his own mind.  “The telegraphone gave me the first hint of the truth,” he said.  “The motion camera brought me a step nearer, but without this third instrument, while I should have been successful, I would not have got at the whole truth.”

He was fingering the apparatus on the library table connected with that in the music-room.  “This is the psychometer for testing mental aberrations,” he explained.  “The scientists who are using it to-day are working, not with a view to aiding criminal jurisprudence, but with the hope of making such discoveries that the mental health of the race may be bettered.  Still, I believe that in the study of mental diseases these men are furnishing the knowledge upon which future criminologists will build to make the detection of crime an absolute certainty.  Some day there will be no jury, no detectives, no witnesses, no attorneys.  The state will merely submit all suspects to tests of scientific instruments like these, and as these instruments can not make mistakes or tell lies their evidence will be conclusive of guilt or innocence.