Law enforcement provides to the Prosecuting Attorney's Office all the evidence gathered about the crime. Typically, a deputy prosecutor reviews the evidence and decides whether to issue formal charges against the defendant and, if so, what the charges should be.
The charging decision is a critical step in the criminal justice process. It is guided by legal and ethical rules that require a reasonable belief that the evidence is sufficient to convince a jury unanimously, beyond a reasonable doubt, and despite any reasonable defenses, that the defendant is guilty of the charge.
The deputy prosecutor may decide not to file formal charges. This could be because there is not enough evidence to charge the suspect or to prove the charge in court, because the deputy prosecutor wants more information before making a decision, or because the case may be more appropriate for another court.