Lauren Baldwin of CriminalDefenseLawyer.com writes that to press charges against someone, a person must contact the police as soon as possible. If the offense is very recent and the perpetrator is still on the scene, he may be arrested immediately. The individual must be arrested before criminal charges can be pressed by either the prosecutor or police.
According to Baldwin, many factors affect whether or not charges can be pressed. If the perpetrator was not at the scene of the crime, a police officer must obtain a warrant from a judge to arrest the perpetrator. Before that can happen, the police must gather evidence of probable cause in order to seek the warrant. This evidence can come from statements from the victim and bystanders, statements from the perpetrator, an assessment of injuries received and physical or recorded evidence of the incident in question. If the accused crime was a misdemeanor or petty crime, the police can file charges in court, which requires the perpetrator to answer for the accused crime. If the accused crime is a felony, then the prosecutor must analyze the police report and determine if there is enough evidence to win a case against the perpetrator. If not, the charges may be dropped.