PRINCIPLES OF INVESTIGATION General Rules.—Hans Gross's rules for guiding investigators are quite generally observed by police detectives assigned to in vestigate crimes. Briefly, they are : Take the simplest view at the outset and disregard all strange and extraordinary supposi tions ; omit the romantic features of fiction writers, remove exag gerations and confine the investigation to bare facts; never follow one idea exclusively; since women play either an indirect or direct part in many crimes and also aid in the concealment and escape of criminals, it is well to look for the woman in the case; search for causes; observe and report on all facts; make comparisons; examine localities with minute care; make measurements of places and things, and take photographs; check statements of witnesses as to time and distance, also memory of events and persons in order to determine whether their statements rest on false suppo sitions; remember there is usually one great blunder which a criminal nearly always commits, especially in big crimes; interview persons who have been employed in the district and know the inhabitants; endeavour to find the victim, relative or interested person from whom the preliminary information regarding the crime can be obtained; never alter the position of, pick up, or even touch an object before it has been minutely described in the report ; note all points where traces of the crime or important details are to be found, e.g., clothing, finger-prints, foot-prints, hair, marks caused by firearms or tools, impressions and stains of all kinds—in short, everything which may have been produced by the criminal and everything which may have been left behind by him. Absolutely everything must be carefully examined, for there is no place where important objects connected with the crime may not be found. Often the strongest proof is found in the smallest details. Foot-prints, traces of blood and forgotten or discarded objects must be protected until experts have had an opportunity to collect or preserve such evidence. The ultimate objective of the examination or interrogation is to give the in vestigator of the occurrence as much detail as if he had been present in person. The investigator must have a wide acquaintance with experts and their capabilities for they are indispensable assistants and their findings and conclusions enable the detec tive to obtain a broader perspective of the case.
Obviously, medico-psychologists are valuable aids of the police, and the types of cases in which they assist cover a very wide field: ante-mortem and post-mortem examinations of wounds; all frac tures and contusions; blood examinations; determination of the cause of illness, death or abnormal behaviour; observation of mental conditions of victims and suspects; and the restoration of decomposed, discoloured, mutilated or mummified remains. In many cases they are able to give the exact race, stature, age and sex from a study of the teeth and skeletal remains. On one occasion, the mutilated and mummified remains of a murdered woman were soaked for three hours in a 1% solution of potas sium-hydrate and then placed in a 2% solution for 18 hours.
After the soaking process, the body was drained and dried, cuts in the cheek were sewed up, cavities in the head and face were stuffed with cotton and then filled with plaster of paris, the filled-in places were smoothed over with flesh coloured embalmer's wax, artificial eyes and hair were placed in position, a missing ear was worked up in wax, flesh tints were added, and eyebrows and lashes painted on. A photograph of the reconstructed body was then taken and easy identification was made possible. Very slight traces of blood may be readily distinguished with the aid of the Dudley Roberts occult blood test. When a stain is defi nitely determined to be blood, the pathologist utilizes the well known precipitin test to discover whether it is human blood or not. A microscopic study of the size, shape and colour of the corpuscles often makes it possible to determine from which par ticular group of animals the blood has come.
The micro-analyst recognizes at a glance all the structures which may appear within the field of the compound microscope and interprets the findings with a reasonable degree of accuracy. Lower plants and animals, plant and animal tissues, vegetable, animal and inorganic fibres, starches, dextrins, sand, soil and minerals are readily identified and their connection with the case under investigation may be quickly established. Dust or stains found in or attached to clothing or weapons, also deposits found under finger-nails, have furnished the investigator with the only and occasionally the most important clue. A single hair from the head of a human being has pointed unerringly to the perpetrator of a felonious offence. The fact that it was human hair, also the age, sex, race, probable colour of eyes, and probable weight of the person to whom the hair belonged, were ascertained by the micro analyst after examining the four structural parts of the one strand that was left behind by the criminal. The hair of every fur bearing animal has its own characteristics and these character istics are so well defined that the expert experiences little diffi culty in determining the type of mammal from which the single strand of fur came (see HAIR).
The chemical analyst is employed in all cases where the in vestigator believes that poison has been given, whether through the mouth or otherwise. He may also supplement the work of the micro-analyst. These experts are able to prove the nature of the substance that was administered and to determine also the nature of organic or inorganic substances that play an im portant part in any criminal investigation. Particles of dust may prove distinctly injurious to some persons and sometimes perfectly healthy people are affected fatally by doses of common drugs or by simple kinds of food. When this occurs, the chemical analyst will discover the true cause of death. Such information has occa sionally cleared accused persons.
Firearms.—Forensic ballistics is that branch of criminal in vestigation which deals with the identification of firearms, bullets, cartridge cases and explosive materials used in guns. Experts in this field study also the effect and trajectory of bullets fired from guns ; they can determine whether a bullet was fired from, or a cartridge case ejected from, a particular firearm. After examin ing a bullet they are able to state the make, calibre, type, approxi mate date of manufacture and the approximate serial number of the gun from which it came. This information is obtained by studying the following points on the bullet :—number of rifling lands, pitch or twist of rifling, width of grooves and lands, depth of grooves, calibre and weight of bullet, and the individual char acteristics which are to be found in the barrel of every firearm, such as rough spots, gouges, imperfections and emery marks. These peculiarities are impressed upon the bullet when fired from the gun.
Identification of cartridge cases discharged from an automatic weapon is made possible by examining the scratches on the side of the case which are produced by the several mechanical opera tions connected with automatic loading and unloading, the marks made by the extractor hook, the firing pin imprint on the primer, the breech face imprint on the primer and shell base, and the imprint of the ejector blade or shoulder. When the cartridge case has been exploded in a revolver, the firing pin and breech face impressions on the primer and shell base furnish means for identi fication. Chemical composition of alloys used in the manufacture of bullets is easily ascertainable from slight traces of the metal, especially if the composition is unusual, while micro- and chemi cal analysis of powder found upon a bullet, even after it has entered a foreign body, has revealed the manufacturer's formula.
To the handwriting expert are referred questioned documents of every description. He studies erasures, obliterations, additions to writing, false seals, water marks, imitations of stains or marks of any character whatever on the paper, age and chemical nature of inks and papers, type of pen or pencil used.
Photography and the Deception Test.—Photography and photo-micrography play an important role in criminal investiga tion. Speaking of the value of the photograph to the criminal in vestigator, Reiss says :—"(i) It constitutes an indestructible docu ment taken automatically which reproduces all the facts and acts as an artificial memory. (2) It is a help to all those called to discharge duties during the trial without knowing the place of the crime. (3) It is able to exercise a psychological effect, whether upon the jury or on the judge. (4) The little details photograph ically revealed upon the place of the crime, such as the foot im pressions, the digital markings, or anything of that nature, aid in the conviction of a criminal or the finding of the one responsible for the crime." Briefly, the camera is employed as a recording agent whenever it is desired to obtain absolute, objective, permanent and easily controlled proofs.
Recently one other tool has been added to the equipment of the investigator: i.e., the psycho-physiological deception test, although it is better known to the public as the "lie-detector." With this technique it is possible to establish guilt or innocence in a com paratively short period, thus avoiding the long, wearisome hours given to the examination of persons who are under suspicion.
The technique of the deception test consists primarily in secur ing a blood pressure curve, taken synchronously with a respiratory and a time curve. In practice, the suspect is seated on a chair, a cuff is then strapped on the upper part of the arm for the purpose of recording the blood pressure and a rubber tube is hooked round the chest for recording the respiration. After adjusting the blood pressure device, the instrument is set in motion and permitted to run for a few minutes in order that the normal reaction for this individual may be obtained. The expert conducting the investiga tion then follows this by an introductory statement to the effect that the suspect is being subjected to a test to determine his guilt or innocence and, further, that taking the test is optional for him. A few questions are then asked which require an answer of "yes" or "no," the correct answers being known to the expert before they are given. The graph, which includes the brief run without ques tions and reactions to the preamble and indifferent questions, is used for comparison with the later record obtained when questions relating to the crime under investigation are asked of the suspect. Results obtained thus far indicate that the deception test (q.v.) affords a convenient and reliable method for detecting deception.
Identification.—Criminal investigation and criminal identifi cation go hand in hand. The identification expert is the foremost ally of the investigator. Occasionally the identification expert fur nishes information to the investigator regarding the identity of the person who committed the crime as well as supplies the evi dence that serves to convict the offender after his apprehension. The duties of the identification expert are (I ) To ascertain identification of the perpetrator of the crime prior to his apprehension (a) by the use of the alphabetical index when the name of the offender is known; (b) by photograph when the criminal has been seen by his victim or by witnesses; (c) by the modus operandi of the criminal ; (d) by the handwriting of the criminal ; (e) by finger impressions left at the scene of the crime.
(2) To ascertain identification of offenders after arrest (a) by the alphabetical index; (b) by a photograph, where no finger prints have been taken; (c) by the modus operandi system con necting the arrested criminal with numerous other crimes; (d) by comparison of the criminal's handwriting with documents con nected with criminal offences; (e) by finger impressions of the criminal found at scenes of crimes committed by him, of which he was not suspected by the investigator; (f) by the ten-digit finger-print system when the offender has been previously recorded in the bureau.
A name registry of convicted criminals marks the beginning of modern criminal identification methods. This registry has served officials effectively and is still used in an amplified form. Quite
early, however, a name registry was found to be comparatively worthless for the purpose of identifying habitual and migratory criminals because they changed their names or residence with every arrest.
The earliest scientific method used for the purpose of criminal identification was photography. In 185o photography made rapid advances with the introduction of the collodion process, for then untrained persons could easily learn how to take and develop photographs. The result was that photographs of criminals were taken in various countries. When photography was introduced, it was believed that this means of identification would furnish a solution to the problem which confronted the law enforcement officials. In the course of a few years, however, the collection of criminal photographs grew so large that it became physically im possible to locate a previous record of the offender. Experts spent weeks in an effort to identify a person suspected of having a prior record. England then started a tattoo registry to supplement the photograph record. This, too, became unwieldy and yielded com paratively small results, considering the enormous amount of labour expended in maintaining and searching the registry.
Measurements of the head: Length of the head. Width of the head. Length of the right ear. Width of the right ear.
Measurements of the limbs: Length of the left foot. Length of the left middle finger. Length of the left little finger. Length of the left forearm.
Bertillon's system has been discarded by most police depart ments, but his descriptive methods are used by investigators be cause no better scheme has yet been devised for furnishing a minutely descriptive, verbal portrait of an individual. Colour of eye, shades of hair and complexion, shape of the forehead, nose and ear, and build of the criminal are subjected to a rigorous but simple classification scheme. Other complementary features in cluded in the verbal portrait are a description of the lips and chin, the general contour of the head, including profile and face, the various modes of implantation of the hair, the beard and the eye brows, the shape of the eyelids, the form and size of the eyebrow and the orbit, the mouth, the wrinkles and furrows of the face, the expression of the physiognomy, also various kinds of informa tion relative to the general aspect of the subject and the visible marks, scars, moles and missing or deformed parts of the anatomy.
A theoretical classification of finger-prints was presented to the University of Breslau by Prof. John Purkinje in 1823. This classification was the foundation of all the theoretical and practical work that followed. Purkenje divided finger-prints into nine basic types. In 1888 Francis Galton made an additional and distinct contribution to the science of dactyloscopia by analysing and counting the papillary ridges in the bulbs of the fingers. His method has been followed by all later investigators. Application of one or two digital impressions as a substitute for signatures and as a means for identification, was made as early as 1858 by Sir William Herschel, head of the Indian Civil Service district of Hooghly, Bengal. The governor-general, in June 1897, directed that the E. R. Henry finger-print system of identification should be adopted in British India. In 1892 the first identification was made from bloody finger-prints left at the scene of a crime. In that year Francisca Rojas, an Argentinian, who had charged a neighbour with the murder of her sons, was found to be the assas sin. The proof of her guilt was established by the bloody impres sions left on the jamb of her door.
Vucetich divides all finger-prints into four primary groups. The first group consists of all those designs formed by curved ridges without angles or deltas, the ridges extending from one side of the finger to the other without recurving. They are called arches. The second group has the angle or delta situated at the right of the person observing it and the directive lines have their exit toward the left. They are called internal loops. The third group has the delta situated at the left of the person observing it and the direction of the lines runs toward the right. They are called the external loops. The fourth group has two deltas and the di rective lines circumscribe circular figures. They are called whorls. For classification purposes the arch, internal loop, external loop and whorl are denominated respectively A. I. E. W. for the thumbs; and 1. 2. 3. 4. for the fingers. Accordingly a hand containing internal loops in the ten fingers would classify I 2222 -I 2222. The total possible primary combinations of the •Vucetich system number 1,048,576.
Primary classification will suffice for the ordinary collection of finger-prints but Vucetich provides for subdivision of large groups in the following classification scheme. Arches : natural arch, 5; internal inclination, 6; external inclination, 7; tented arches, 8. Internal loops : natural, 5; converging ridges, 6; approximating central pockets, 7 ; irregular loops, 8. External loops: natural, 5; converging ridges, 6; approximating central pockets, 7 ; irregular loops, 8. Whorls : natural, 5; lateral pockets and twinned loops, 6; elliptical whorls, 7; accidental or irregular types, 8.
E. R. Henry divides all impressions into four types, namely: arches, loops, whorls, composites. (I) In arches, the ridges run from one side to the other without backward turn or twist and, ordinarily, have no delta. (2) Loops have at least one recurving ridge and at least one ridge between the delta and core. In ulnar loops the ridges recurve toward the little finger; in radial loops, the ridges recurve toward the thumb. (3) Whorls have at least one ridge making a complete circuit. (4) Composites are patterns having characteristics of two or more of the foregoing patterns.
The primary classification is arrived at by pairing off the fingers. Beginning with the right thumb they occur on the finger-print sheets thus: first pair, right thumb and index are given a value of 16; second pair, right middle and ring fingers, a value of 8; third pair, right little finger and left thumb, a value of 4; fourth pair, left index and middle fingers, a value of 2; fifth pair, left ring and little fingers, a value of 1; the first of each pair counting as the denominator and the second as the numerator. Only whorls or composites are given a valuation. One is added to the numer ator and denominator, thus giving 1 over i where all patterns are arches or loops, and 32 over 32 where all patterns are whorls or composites.
Arches, tented arches, radial or ulnar loops occurring in either of the index fingers compose the sub-classification, the right index finger being the numerator and the left index the denominator.
A group classification is obtained by tracing the ridges in the whorls and counting the ridges in the loops of the index and middle fingers of both hands. Arches, tented arches and radial loops, being of relatively infrequent occurrence, are always noted. in the formula.
Owing to the fact that it was difficult to discover the identity of a person from a single finger impression left at the scene of the crime, even though the criminal's finger-prints were filed in the identification bureau, identification experts decided to give atten tion to the classification of single finger-print impressions. Oloriz, in Spain, was a pioneer in this field, followed by Jorgensen in Denmark, Collins in England, and Crosskey and Larson in the United States. These investigators have succeeded in producing single finger-print systems that are operating in various countries. Their formulae make it possible to identify a criminal from a single digital impression which may be left behind by the criminal, provided that the offender's prints have been previously regis tered and are in the single finger-print file.
Larson System.--The following is a brief outline of the Larson system. The pattern to be identified is (I) classified according to the gross configurations of characteristic formations; arches are divided into seven types ; loops, 9; whorls, 6; twinned loops and lateral pockets, 4; and accidentals, 13. (2) The inclination of the pattern—i.e., the pattern slopes to the right or left, or has no inclination at all—divides all types into three sub-divisions. (3) The pattern is then classified according to the configuration of the ridges which constitute the core. (4) The ridge surrounding the core—called by Larson, the "envelope"—is classified according to its peculiarities or appendages. (5) The first ridge in front of the delta is classified according to its characteristics, such, for example, as abrupt terminations, tented, composite characteristics, dotted ridges, forked, natural or recurving. (6) The delta is then classified according to two basic types: open and closed. These two types are further divided into eight sub-types. (7) The final differentiation is reached by ridge counting and ridge character istics. Larson says : "The pattern is split into natural divisions and each division may be treated independently. Thus a pattern may be searched for according to type; core; envelope; delta; ridge count ; or ridge characteristics." Analysis of Handwriting.—Such a large amount of hand writing in the form of signatures on pawnshop and second-hand store books, hotel registers, writing found on worthless cheques, letters and documents of every character, is connected with crim inal cases that it was necessary to find a means of classifying this valuable material. Dr. Hans Schneickert in Germany, several Aus trian experts, and Lee and Abbey in the United States have con tributed to this important method of identifying criminals.
The chart used by Lee and Abbey is in the adjoining column.
Modern identification bureaux, or divisions, maintain elaborate indexes giving the alphabetical arrangement of names according to the directory guide system ; the modus operandi, arranged either by index guides or decimal system ; a special marks file, in which are kept the anatomical peculiarities that assist in identifying indi viduals; and the ever-present "rogues' gallery." In some cities the "rogues' gallery" photographs are pasted in books kept in numerical order; in others, they are kept in books but filed according to crime ; and in still others they are placed in books and segregated according to crime, then according to hair colour, eye colour, height and weight. Some departments use the Kardex system and file photographs according to the modus oper andi of the criminal, and then by the English descriptive method. Others have large wall leafs on which are placed the photographs of active operators, and these are frequently arranged according to description of the individual and his modus operandi.
While it is true to-day that not many identifications are made by photographs, they are yet sufficient in number to warrant their continuance as a means of identification.