Prosecutors are the attorneys representing the interests of the state in every criminal proceeding.
If/When Prosecutors decide that they have enough evidence, they will decide what crime to charge the suspect with.
Prosecutors are also able to negotiate the charges and sentences with suspects and their lawyers.
If there isn’t enough evidence, and a prosecutor declines a case, the suspect will be released.
If the suspect enters the legal system many hearings will be had before an actual trial is conducted.
During these hearings lawyers will argue their motions and admissibility of evidence.
Juries in some cases, will ultimately decide if a defendant is guilty or innocent.