The records of the police and of the private agencies contain many instances where murderers have confessed their guilt long after the crime to supposed friends, who were in reality decoys placed there for that very purpose. It is a peculiarity of criminals that they cannot keep their secrets locked in their own breasts. The impulse to confession is universal, particularly in women. Egotism has some part in this, but the chief element is the desire for companionship. Criminals have a horror of dying under an alias. The dignity of identity appeals even to the tramp. This impulse leads oftentimes to the most unnecessary and suicidal disclosures. The murderer who has planned and executed a diabolical homicide and who has retired to obscurity and safety will very likely in course of time make a clean breast of it to some one whom he believes to be his friend. He wants to “get it off his chest,” to talk it over, to discuss its fine points, to boast of how clever he was, to ask for unnecessary advice about his conduct in the future, to have at least one other person in the world who has seen his soul’s nakedness.

The interesting feature of such confessions from a legal point of view is that, no matter how circumstantial they may be, they are not usually of themselves sufficient under our law to warrant a conviction. The admission or confession of a defendant needs legal corroboration. This corroboration is often very difficult to find, and frequently cannot be secured at all. This provision of the statutes is doubtless a wise one to prevent hysterical, suicidal, egotistical, and semi-insane persons from meeting death in the electric chair or on the gallows, but it often results in the guilty going unpunished. Personally, I have never known a criminal to confess a crime of which he was innocent. The nearest thing to it in my experience is when one criminal, jointly guilty with another and sure of conviction, has drawn lots with his pal, lost, confessed, and in the confession exculpated his companion.

In the police organization of almost every large city there are a few men who are genuinely gifted for the work of detection. Such an one was Petrosino, a great detective, and an honest, unselfish, and heroic man, who united indefatigable patience and industry with reasoning powers of a high order. The most thrilling evening of my life was when my wife and I listened before a crackling fire in my library to Joe’s story of the Van Cortlandt Park murder, the night before I was going to prosecute the case. Sitting stiffly in an arm-chair, his great, ugly moon-face expressionless save for an occasional flash from his black eyes, Petrosino recounted slowly and accurately how, by means of a single slip of paper bearing the penciled name “Sabbatto Gizzi, P. O. Box 239, Lambertville, N. J.,” he had run down the unknown murderer of an unknown Italian stabbed to death in the park’s shrubbery. The paper contained neither the name of the criminal nor his victim, but by means of this slender clue he had gone to Lambertville and found an Italian who had identified the deceased as a man who had left Lambertville for New York in the company of another Italian named Strollo. Petrosino interviewed Strollo, who admitted the trip but denied any knowledge of his companion’s death. He had, he said, turned him over to his brother, for whom Strollo had been searching.

In Strollo’s pocket Petrosino found a letter to the brother from Tony Torsielli, the murdered man. It was in Strollo’s own handwriting and enclosed in an envelope addressed to Torsielli himself at Lambertville. This envelope bore a red two-cent stamp. On the basis of this letter, aided by Strollo’s contradictory statements, Petrosino reconstructed the murder and demonstrated that there was no brother, that Strollo had invented him for the purpose of luring Torsielli to New York, and that he had acted as amanuensis for Torsielli and carried on the correspondence for both. The envelope addressed in Strollo’s handwriting to Torsielli at Lambertville was the key to the whole mystery. There was no reason why Strollo should be writing to his own friend whom he saw daily and who lived beside him in the same town. Neither, argued Petrosino, would there be any reason for putting on a two-cent stamp in a place so small as to have no mail delivery. Ergo, the envelope must have been intended to create the impression that it had been mailed from some other place, by another person—from whom but the fictitious brother? Bit by bit Petrosino built up a case entirely out of circumstantial evidence that demonstrated Strollo’s guilt to a mathematical certainty. So vivid was Petrosino’s account of his labors that in opening the case next day to the jury I had but to repeat the story I had heard the night before. Strollo was convicted after a week’s trial before Judge O’Gorman in the Criminal Term of the Supreme Court and paid the penalty of his treachery in the electric chair. For him I felt not one pang of pity or remorse.

But during the preparation for the case the function of the detective as a decoy was demonstrated in a most effective manner. Strollo was confined in the House of Detention and a detective from head-quarters was introduced there as an ostensible prisoner, under the name of Silvio. Strollo and he became great friends, and when the former was removed to the Tombs the murderer wrote elaborately to the detective, requesting him to testify as a witness at the trial on his behalf and instructing him what to say in order to establish an alibi. Those letters were the last nails in Strollo’s coffin. After his conviction they were stolen by somebody and could not be included in the case on appeal, for which reason the court had some doubt as to whether the conviction should be affirmed. Before the Court of Appeals rendered its decision, however, I found, while cleaning out my safe, photographs of the letters which I had had taken as a precautionary measure, but the existence of which I had forgotten. I now have every important document that comes into my hands as evidence photographed as a matter of course.

Petrosino’s physical characteristics were so pronounced that he was probably as widely, if not more widely, known than any other Italian in New York. He was short and heavy, with enormous shoulders and a bull neck, on which was placed a great round head like a summer squash. His face was pock-marked, and he talked with a deliberation that was due to his desire for accuracy, but which at times might have been suspected to arise from some other cause. He rarely smiled and went methodically about his business, which was to drive the Italian criminals out of the city and country. Of course, being a marked man in more senses than one, it was practically impossible to disguise himself, and, accordingly, he had to rely upon his own investigations and detective powers, supplemented by the efforts of the trained men in the Italian branch, many of whom are detectives of a high order of ability. If the life of Petrosino were to be written, it would be a book unique in the history of criminology and crime, for this man was probably the only great detective of the world to find his career in a foreign country amid criminals of his own race.

I have instanced Petrosino as an example of a police detective of a very unusual type, but I have known several other men on the New York Police Force of real genius in their own particular lines of work. One of these is an Irishman who makes a specialty of get-rich-quick men, oil and mining stock operators, wire-tappers and their kin, and who knows the antecedents and history of most of them better than any other man in the country. He is ready to take the part of either a “sucker” or a fellow crook, as the exigencies of the case may demand.

And then there was old Tom Byrnes, of whom everybody knows. There are detectives—real ones—on the police force of all the great cities of the world to-day, most of them specialists, a few of them geniuses capable of undertaking the ferreting out of any sort of mystery, but the last are rare. The police detective usually lacks the training, education, and social experience to make him effective in dealing with the class of élite criminals who make high society their field. Yet, of course, it is this class of crooks who most excite our interest and who fill the pages of popular detective fiction.

The head-quarters man has no time nor inclination to follow the sporting duchess and the fictitious earl who accompanies her in their picturesque wanderings around the world. He is busy inside the confines of his own country. Parents or children may disappear, but the mere seeking of oblivion on their part is no crime and does not concern him except by special dispensation on the part of his superiors. Divorced couples may steal their own children back and forward, royalties may inadvertently involve themselves with undesirables, governmental information exude from State portals in a peculiar manner, business secrets pass into the hands of rivals, race-horses develop strange and untimely diseases, husbands take long and mysterious trips from home—a thousand exciting and worrying things may happen to the astonishment, distress, or intense interest of nations, governments, political parties, or private individuals, which from their very nature are outside the purview of the regular police. Here, then, is the field of the secret agent or private detective, and here, forsooth, is where the detective of genuine deductive powers and the polished address of the so-called “man of the world” is required.

There are two classes of cases where a private detective must needs be used, if indeed any professional assistance is to be called in: first, where the person whose identity is sought to be discovered or whose activities are sought to be terminated is not a criminal or has committed no crime, and second, where, though a crime has been committed, the injured parties cannot afford to undertake a public prosecution.