The signed and submitted by the police describes the nature of the crime and the probable cause, stating the role of the suspect.

I think the answer is the evidence or statement. I am not really sure what you are trying to ask but if this was a question he answer would be either evidence or statement.

The contain of the document can tell us that the document related is the Police Case File.

Explanation:

This file contains all about an specific crime or offense that someone did. It is described the nature of crime, the probable cause, role of the suspect and any witness statement or a third party declaration.