Finally, I would thank the proprietors of _Knowledge_ and the Editor, Mr. Wilfred Mark Webb, for the loan of various blocks and for permitting me to make use of material from several articles of mine on handwriting, which have appeared in that journal. C. A. M. _White Cottage, Amersham Common, Buckinghamshire._ CONTENTS PAGE CHAPTER I INTRODUCTION Conflict between the Law-maker and the Law-breaker-- Illustrations of Deductive Reasoning in Criminal Cases-- Scientific Evidence--Scientific Assistance for the Accused--Instances of Advantages of Conflict of Scientific Evidence--Scientific Partisanship 1 CHAPTER II DETECTION AND CAPTURE OF THE CRIMINAL Contrasts between Eighteenth, Nineteenth and Twentieth Centuries--Margaret Catchpole--Tawell--Crippen--Portraits and the Press--Charlesworth Case--Bloodhounds--Police Dogs--Circumstantial Detection 22 CHAPTER III PERSONAL IDENTIFICATION McKeever's Experiment on Fallibility of Eye-witnesses-- Gorse Hall Murder--Cases of Mistaken Identity--Gun-flash Recognition--Self-deception--Tichborne Case 37 CHAPTER IV SYSTEMS OF IDENTIFICATION Photography--Anthropometry--Finger-prints and their Uses 48 CHAPTER V IDENTIFICATION AND HANDWRITING Heredity--Emotional Influences--Effects of Disease on Handwriting 70 CHAPTER VI EVIDENCE AS TO HANDWRITING Illustrative Cases--Handwriting Experts 85 CHAPTER VII FORGED DOCUMENTS Use of Microscope--Erasures--Photographic Methods-- Typewritten Matter--Examinations of Charred Fragments-- Forgery of Bank Notes 93 CHAPTER VIII DISTINGUISHING INKS IN HANDWRITING Elizabethan Ink--Milton's Bible--Age of Inks--Carbon Inks--Herculaneum MSS.--Forgery of Ancient Documents 105 CHAPTER IX TWO NOTABLE TRIALS Trial of Brinkley--Trial of Robert Wood 116 CHAPTER X SYMPATHETIC INKS 130 CHAPTER XI REMARKABLE FORGERY TRIALS Trials--William Hale--The Perreaus--Caroline Rudd--Dr. Dodd--Whalley Will Case--Pilcher, etc. 135 CHAPTER XII IDENTIFICATION OF HUMAN BLOOD AND HUMAN HAIR Structure of Blood--Human Blood--Blood of Animals--Blood Crystals--Libellers of Sir E. Godfrey--Trial of Nation in 1857--Physiological Tests--Precipitines--First Trial in France--Gorse Hall Trials--Human Hair--Hairs of Animals 154 CHAPTER XIII EARLY POISONING TRIALS