Where a murder is committed by a method that destroys its own evidence or fails to leave what might be called a "trace" or clue detectives are hampered but not necessarily baffled. In these cases, almost without exception, it is circumstances that bring the criminal to punishment. While a jury might refuse to convict on circumstantial evidence a detective is not so deterred. The scientific detective turns science against the scientific murderer. He batters the suspect with circumstantial evidence until in nine out of ten cases the scientific suspect weakens and acknowledges his crime. Circumstantial evidence backed by a confession that checks on all angles is about all any jury needs to be convinced of guilt.
When your correspondent began to dig into this subject of artistic or scientific murder Government detectives—themselves master scientists—made a request. They asked that we be "a little vague" in the use of proper names and in description of the eighteen murder methods most difficult of detection. So, we will name no chemicals or poisons but confine ourselves to effects and processes.
The commonest method is the complete destruction of the corpse—the corpus delicti. Cremation is the usual means resorted to. The body is burned in a furnace or on a pyre. Effort is sometimes made to make identification impossible by burning the body or parts of it in gasoline flames. The scientist has no edge on his uneducated fellow in this type of murder case. He practically never is able to remain with the burning corpse long enough to do a perfect job.
In many cases complete dissolution of the corpse is attempted by immersion in acids. There are acids that completely dissolve bone tissue and even clothing but circumstances usually reveal these crimes. Accessibility to such chemicals and procurement of such chemicals usually lead to a search. The search usually leads to the finding of bone fragments, identifiable by means of buttons, bits of jewelry, metallic dentistry and other bits of evidence which escapes or rather resists the acid effects.
And now we get into some deep scientific water. It is actually possible by the exact and accurate dosage of a certain poison, over a long period, to produce death "by typhoid fever." This poison, a common and easily available one shows up like an electric sign when not scientifically administered. But when given in frequent and exact small quantities it produces every symptom of typhoid. Quite often the corpse is buried as a typhoid victim.
In most of these "typhoid" cases the motive is insurance and the murderer encouraged by success in one case attempts others. Sometimes there are a score of victims. In practically all cases the murderer is convicted in the long run. The circumstances that usually bring about detection are doctors and nurses and neighbors. They will remember that the murderer was always quite enthusiastic about insurance. A nurse will remember that the murderer insisted on preparing the victim's food. Sometimes a druggist will remember selling some poison to kill a dog or as an insecticide.
There is, too, a gas that administered in exactly correct quantities will produce "tuberculosis." This gas kills instantly unless scientifically administered. A small quantity will cause the lungs to "rot" gradually bringing death in from five to thirty days with all the symptoms of rapid or "galloping" consumption. Doctors have so diagnosed such cases but circumstances usually bring the crime to light. First among these is that the gas is rare, ordinarily. It can be home-made but only by a chemist with a well-grounded knowledge.
It would appear that, among poisons, the most powerful would be the hardest to detect. This because a small dose would leave less trace than a large one. It follows only in some cases. One very powerful poison absolutely defies detection. Another, and the most deadly poison known to man reveals itself instantly. This second poison perfumes the corpse and leaves it smelling with a fruity odor. Any doctor or chemist can identify it instantly regardless of how small the dose might have been.
In the event of the first named powerful poison—the one that defies detection—there is no odor or other discernible indication of any nature. When scientifically administered the fatal dose is less than one billionth the weight of an ordinary human body. Thus, to trace it, the autopsy doctors would have to find, separate or segregate a billionth bit of the mass under observation. The body completely absorbs the fatal chemical and so—.