Each jurisdiction has its own rules regarding the following procedures.

In the U.S., a judge may issue an arrest warrant to "take the body of the person" into custody if there is a reasonable belief that a crime was committed by the person identified. Both the crime and the person alleged to have committed it must be identified specifically in an arrest warrant.

The description of either the crime or the criminal, or both, is made by witnesses whose statements are given under oath. Typically, the affiant is a law enforcement officer, but additional witness affidavits are used when necessary.

Examples of a forensic science expert's affidavit, which may be included in the evidence upon which an arrest warrant is based:

Example 1: Identification and description of a person's genetic profile, obtained through forensic DNA typing of a known subject and crime scene evidence.

Example 2: An affidavit identifying a subject on the basis of matching known fingerprint standards (e.g., 10-print card) with latent prints of value lifted from a crime scene.

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