Which document is used by an agency to detain a subject in custody who is wanted?

The document that is utilized by an agency to detain a subject in custody who is wanted is known as a detainer. This legal instrument essentially informs law enforcement agencies that there is a hold on an individual, typically because that person is wanted for criminal charges or has violated the terms of probation or parole.

Detainers ensure that when the individual is apprehended or is already in custody for another reason, they cannot be released until the authority that placed the detainer can take further action, such as bringing them in for an outstanding warrant or additional charges. This helps maintain public safety by preventing the immediate release of individuals who may pose a risk or have unresolved legal matters.

In contrast, an affidavit is a written statement confirmed by oath or affirmation, usually used as evidence in legal processes. An indictment is a formal charge or accusation of a serious crime, often resulting from a grand jury's decision. Modification typically refers to changes in orders or conditions but does not function as a tool for detaining individuals. Thus, the detainer is specifically designed for the purpose of establishing custody over wanted individuals.