1920s Forensics

(an excerpt from the Call of Cthulhu 1920s Investigator’s Companion)

Forensic Scientist

A forensic pathologist of the 1920s had much in common with their predecessor of the 1890s. They still worked long hours at a gruesome and difficult job. They were still underpaid. But they had better tools to work with. The microscope had been greatly improved to show more detail more clearly. The spectroscope, strictly experimental in the 1890s, was now able to identify brands of gunpowder or unusual chemicals. The chemicals used in forensic testing were more refined and less prone to error-making contamination. When in doubt, the pathologist now had educated peers from whom to ask advice. The pathologist no longer practiced a science of his own devising: they had colleagues and probably students as well.


1920s bullet weights

Charles E. Waite, of the New York State Prosecutor’s Office, was the first person to collate ballistic data, analyzing guns from both home and abroad. His studies made it possible to use slugs and spent cartridges to identify the particular gun from which a bullet was fired. By 1922 Waite’s work resulted in the formation of the New York Bureau of Forensic Ballistics. Here Phillip Gravelle adapted the comparison microscope to ballistic use while John Fisher invented the helixometer used to closely examine the interior of gun barrels.

Accurate identification depends on the condition of the slug retrieved. Usually the caliber can be determined by size and weight. Even the specific make of gun might be identified, using the pattern of microscopic grooves left on the slug by the rifling of the pistol or rifle. Some slugs are so damaged that even accurate identification of caliber is difficult. Note that shotgun slugs or pellets bare no specific marks. However, shotgun casings may bear marks from the weapon’s firing and ejection mechanisms, allowing for a possible match.

In the case of a shooting death, the distance from which the weapon was fired can often be gauged by evidence found near the wound, sometimes an aid in determining whether a death was suicide or murder. A star-shaped burst in the skin around the wound indicates the muzzle was held directly against the body when fired. Soot smudges, easily wiped away, are usually found when the weapon was discharged less than twelve inches from the victim. At longer distances, sometimes up to three feet, the skin is “tattooed” by small powder burns that do not wash or wipe away. Sometimes it was possible to analyze the powder and determine the manufacturer.

Establishment of Blood Types

Karl Landsteiner

In 1901, Karl Landsteiner discovered the four basic blood types: A, B, AB, and O. Landsteiner’s research was originally intended to prevent violent reactions to blood transfusions. Like the precipitin test, blood-typing tests relied on one type of blood reacting against another. Type A blood reacted against type B blood by forming a clot, and vice versa. AB blood reacted against no other type, but all other types reacted against it. Type O reacted against any other type, but was never reacted against. A given bloodstain had to be tested twice (for both blood types A and B) and the tests might have to be repeated two or three times to confirm the results, so a lot of blood was required. Only the four blood types were known in the 1920s. The Rh factor was unknown until 1940.

Blood typing was not used as a law enforcement tool until 1923 when the Italian, Latte, discovered an easy method for checking blood type using only the smallest of samples. After using his method to solve a couple of baffling cases, a conference held in West Germany in 1926 publicly recognized the usefulness of Latte’s methods.

By 1925 Japanese researchers are discovering that a large percentage of the population are “secretors,” people whose blood type can be determined from samples of other bodily secretions including saliva and semen. A Japanese murder is solved in 1928 using this knowledge. It should be noted that secretion samples must be reasonably fresh to produce reliable results.

In America, it is 1934 before the first major police chemical and toxicological laboratory is established in New York, and 1938 before the first serological laboratory is equipped to study bloodstains in the manner pioneered by European criminologists.

Still of limited use are the thousands of blood spatter samples created by the Frenchmen, Florence and Fricon. These cards show examples of blood that has been dripped, splattered, sprayed by artery, or thrown by different sorts of weapons.

The Fingerprint Registry

Fingerprint Pattern

Also in 1901, Edward Henry was made Assistant Commissioner of Scotland Yard’s criminal investigation Department. He wasted no time in introducing a fingerprint registry system which he had developed in India while serving as Inspector General of Police. His system was similar to Vetuchich’s, but differed in one vital respect: under Henry’s system, each fingerprint was described numerically.

That is, each of the four kinds of fingerprint was assigned a number. Another number indicated how many ridges the print had, yet another indicated their spacing, still another the type and location of scars or other notable features, and so on. In the end, each print was described by a long formula, and could be filed numerically. If a fingerprint was found at the scene of a crime, its formula could be quickly worked out and it would then be compared with known prints having the same or very similar numbers. This might be as few as ten or fifteen print sets out of a file of thousands.

In its first year, Edward Henry’s fingerprint registry identified 1,700 criminals, thrice as many as the Bertillon system in use the previous year. By 1920, Henry’s system was used all over the world. The Bertillon system was discarded. Only the useful scaled photographs survived.

Police took prints of every person who was arrested, even on the most trivial offense, in case the prints showed up later. Investigators who are arrested (not necessarily convicted) for any reason had best beware: the police just might take fingerprints from all those pickaxes and shotguns found in the old cemetery.


Crime scene photography

Photography was proving even more useful in police work. Detectives were better-trained in the use of a camera, and the camera itself was lighter, sturdier, and more reliable. In the darkroom, photographers experimented with developing techniques to extract more information from a photograph. They might increase contrast to distinguish between vague details, such as wrinkles and bloodstains on a pillow, for instance, or they might enlarge part of a photograph to reveal details of a man’s face.

Photography using X-rays (radiology) and ultraviolet light (fluoroscopy) usefully supplemented visible-light photography: visibly similar substances often reflected radiation of different wavelengths differently. For instance, detectives might be faced with two seemingly identical documents, one genuine, the other a modern forgery. One paper might glow brightly under ultraviolet light while the other did not. Metals in modern inks blocked X-rays; natural inks would not. In addition, X- rays could be used to inspect suspicious packages or fragile corpses. Ultraviolet light could reveal the presence of dried stains, including blood, semen, or urine. Even thoroughly laundered blood, undetectable by any other means, could be spotted under ultraviolet light.

Some police departments employed stereoptic (3-D) cameras, which had been used during World War I to pinpoint factories and other installations. They were of some use in forensic analysis. Triangulating the double camera images ended any dispute about size, distance, or location. Unfortunately, 3-D photography has always had a spotty history, and the technique was never widely used.

Other Kinds of Evidence

Human hair was still a dubious clue. In a few cases hair similar to the victim’s was found on the suspect, and hair similar to the suspect’s on the victim. This was considered extremely convincing evidence. Pubic hair was particularly damning.

An English murderer is convicted on the basis of soil samples taken from his shoes and matched to soil from the murder scene. A report on the investigation, outlining methods of soil identification, is published in 1918. In France, a murderer confesses to a crime when presented with evidence of his involvement gained from examining the dust on his clothing. In Berkeley, California, a vacuum cleaner is being used to accumulate microscopic evidence before 1920.

Dental records had been used to confirm the identity of some victims, but no one had been identified on the basis of dental records alone. Dentition had never been used to identify a murderer. Styles of laundry marks and laundry mark codes—indelible abbreviations on the inside of collars, etc., still used by many commercial laundries to identify the ownership of garments once they have been cleaned—were handy in identifying John/Jane Doe victims. Since some customers disliked having numbers stamped all over their clothes, some laundries began using invisible ink, which could be revealed under an ultraviolet light.

Handwriting was being studied extensively in the 1920s. An expert could determine whether two documents had been written by the same person, even if the handwriting were disguised. He might be able to deter mine a writer’s education and psychological constitution. Police departments throughout the world recognized the effectiveness of undercover agents and informants, techniques pioneered by Scotland Yard in the late 1890s.

Investigators in disguise or with appropriate foreign language skills might be approached by police detectives for help on a case. This is a good way for investigators to get minor criminal offenses off the books. Trading aid for the dropping of charges is a typical informer ploy.

Public appeals for help always enjoyed some success, especially if a reward was offered. Motion-picture theaters made this technique even more effective. Along with previews and news clips, movie-goers might be treated to a picture of a murder victim, as well as with an appeal for clues to his or her identity.


1920s Forensics

Cthulhu Supremus Est FrankSirmarco