Definition - What does Criminal Complaint mean?
A criminal complaint is when someone makes a formal pleading in the form of a document which begins the process of prosecuting the criminal. In criminal cases, it is almost always the government who files the complaint. This is opposed to civil complaints, which are often filed by ordinary citizens. It is usually the prosecution who files the criminal complaint.
Justipedia explains Criminal Complaint
When a person is arrested, that does not automatically start the legal process of prosecuting and sentencing. Instead, a document must be filed which lays out the accusations against the person. This document is the criminal complaint. Once the criminal complaint is filed, the prosecution can begin preparing to bring the person to justice. A criminal complaint is sort of like a starting bell for the legal process to begin.