It is accomplished by the two or three per cent. of real detectives on the force.
For instance: A burglary has been committed. Part of the stolen articles have been traced to a pawnshop. The pawnbroker describes the man who pledged them, but the description might fit any one of a hundred professional crooks. He does not recognize any of the Rogues Gallery portraits as that of the man from whom he received the goods. Pawnbrokers seldom identify crooks, for it is to their interest to plead a bad memory in this respect.
But Detectives Burke and Duvaney ascertain from one of their "stool pigeons" that Michael Ribbs, alias Padlock Mike, is in funds—that he and his "moll," who may be his wife or his mistress, are enjoying the fruits of Mike's labors. And as Mike's specialty is burglary, Chief Manning rightfully decides that he is responsible for one or more of the recent robberies.
From this point the real detective work begins. The chief assigns two of his really capable men, not to solve any one of the numerous burglaries that have been reported, but to ascertain the recent doings of Padlock Mike and to obtain evidence—legal evidence that will stand the test of the courts—with which to send the criminal to jail. And the chances are that in convicting Mike, half a dozen mysterious burglaries will have been solved.
This is the ordinary routine of detective work. Of course, there are innumerable variations, and yet not as many as most people imagine. About eighty-five per cent. of the detective force is constantly employed at this routine business, while fifteen per cent., or even less, is engaged on work that is not in a large measure mechanical.
As for Chief Manning, his genius for directing his subordinates is inconspicuously employed all the time. But occasionally a more exacting demand will be made on it. It may be in a homicide case in which a wife has poisoned her husband.
Of course, in a case of this sort, "stool pigeon" men are useless, for no professional crooks are involved. So Manning assigns six or seven of his best men to the case. They do not roam about promiscuously, treading on one another's toes. To each is given a phase of the case to develop and he reports as frequently as possible to the chief. At the end of four weeks Manning, surveying the reports of his men, finds himself in possession of the following:
The chemical analysis of the vital organs shows that the victim died of arsenic poisoning. Detectives have discovered the druggist who sold the poison to the wife. Other detectives have turned in competent evidence tending to establish the woman's dislike of her husband. Moreover, she was in love with another man in whose company she was frequently seen. Then it is found that the husband's life was insured and his death not only released her from matrimonial ties which had become irksome, but also netted her a considerable sum in cash.
Sufficient motive for the crime has now been established. The poison of which the husband died has been traced directly to the wife. But a vital element of the case is still missing. It is necessary to prove that the wife had exclusive opportunity to administer the drug.
Manning now concentrates all his energies toward this end. Obviously, all the deductions of Messrs. Lecocq and Sherlock Holmes would be futile. But through shrewd questioning of the servants in the house he ascertains that the husband was taken violently ill after supper and that no guests were present at the meal.