Hugo Gernsback — founder of the first sf magazine, coiner of the phrase “scientifiction,” namesake of the Hugo Award — on writing science fiction, from 1930:
(1) A Scientific Detective Story is one in which the method of crime is solved, or the criminal traced, by the aid of scientific apparatus or with the help of scientific knowledge possessed by the detective or his coworkers.
(2) A crime so ingenious, that it requires scientific methods to solve it, usually is committed with scientific aid and in a scientific manner. Therefore the criminal, as well as the detective, should possess some scientific knowledge. You will see that this is not an absolute essential to a good story; a scientific detective can use science in tracing the perpetrator of an ordinary crime, but judicious use of science by both criminal and detective heightens the interest because it puts the two combatants on a more equal plane.
(3) As most of our readers are scientifically minded, the methods used by criminal or detective must be rational, logical and feasible. Now, this does not limit the author’s imagination; he can develop many imaginative uses of science, provided they are reasonable. For example: one author sent us a story of a man who rendered himself invisible by painting his clothes and face with a non-light reflecting paint. By explaining some of the laws of light and color he made this accomplishment sound plausible, as indeed it is. But he forgot to mention the shadow which is naturally cast by any object standing in the light, whether or not it is visible to our eyes. Readers of our magazine pick us up on these little details. To avoid such mistakes in writing, which really arise from lack of thought, consider your story from every angle before you write your final copy.
(4) What description of clouds and sunsets was to the old novelist, description of scientific apparatus and methods is to the modern Scientific Detective writer. Here again the author must remember that his work will be read by competent scientists among our readers; and, without careful reference to the encyclopedia, no descriptions of scientific instruments should be included in your stories. If you are not in touch with a Public Library, it is advisable to buy a few really good reference books. Criminoscientific fiction has come to stay and your investment will pay you dividends.
(via Schism Matrix)