The way a criminal charge is filed can vary and is a process that takes place in stages. Generally the most common way a criminal charge is brought against someone is through a police investigation. The police may either respond to a call or observe suspicious activity. The police will complete an investigation and determine if criminal charges should be pursued. Depending on the nature of the crime the police may make an arrest which results in criminal charges being filed. In some instances police will consult the State’s attorney to determine if charges should be filed. In either instance once the determination is made that is sufficient evidence that a crime has been committed then criminal charges are filed.
Another way criminal charges may be filed is if another citizen pursues charges against someone. The majority of the time this is done by someone calling the police to investigate but a citizen may also speak with a magistrate. The individual citizen may present their evidence to the magistrate that someone has committed a crime and the magistrate will decide whether or not to issue a warrant. The evidence presented is generally just going to be oral testimony. However if the magistrate does decide to issue a warrant then it is up to the State what to do with the charge, not the individual who originally pursued having criminal charges pressed against someone else.
If you have had criminal charges filed against you it does not mean you are guilty. A criminal charge is basically just an accusation. This accusation must be proven at trial and many times the case against the accused can be defeated in court.