She was to all intents and purposes a police spy living the life of the class upon whom she was spying, and for certain reasons enjoying their confidence.
The professional informer or "nark" is rarely suspected. Personal communication with the authorities is avoided as much as possible. Sometimes, in order to put a desperate gang off the scent, the spy who has been in close relationship with them is arrested too, and discharged on account of "insufficient evidence" to implicate him.
To the student of humanity even more interesting than the professional informers are the honest people who become possessed of information with regard to criminal deeds, and from conscientious motives hold their peace.
The Roman Catholic clergy never, of course, betray that which they learn under the seal of confession. But it sometimes happens that terrible secrets are learnt by Protestant clergymen, Salvation Army workers, doctors, and nurses.
A fierce press discussion raged some years ago around the action of a Salvation Army captain to whom a crime was confessed by a penitent, and who went straight away and gave information. Some people held that the action was justified, others that the confession was made in circumstances which did not justify its betrayal.
After the conviction of Israel Lipski for the murder of a Jewess in the East End there was considerable doubt as to his guilt. It looked for a time as if he was likely to be reprieved. A Jewish Rabbi, to whom Lipski had already confessed, kept the secret inviolate until the Home Secretary had refused the petition. The Rabbi knew the man was guilty, but he felt he had no right to use his confession against him.
The secrets of many of the mysteries which have baffled the police are in the possession of men and women who for one motive or another hesitate to reveal them.
The reason for silence is sometimes relationship to the guilty person. A wife cannot be expected to give her husband to the gallows, a father or mother cannot be expected to speak the word which would send a son to a shameful death.
So all the time they keep the ghastly secret and live in constant terror that some day the truth may be discovered.
But most criminals are "given away" sooner or later by informers. How many are thus handed over to justice the public have no means of estimating. The police rule is to screen the "nark" at all hazards. The moment an informer is put in the witness-box his value as an instrument in the detection of crime is destroyed for ever.