That said, anyone can go before a Justice of the Peace and seek to have a charge laid against someone. Most commonly these are charges for assault although almost any criminal case can start this way.
There is a two step process to laying a private information.
First, the complaint appears before a Justice of the Peace and gives a sworn statement. That statement must set out the elements of a recognized criminal charge. The Justice of the Peace, once satisfied there is a charge available in proper form accepts the charge and adjourns the matter to a second stage hearing.
The second stage hearing, usually heard before a Justice of the Peace (although sometimes a judge conducts the hearing) is far more detailed and takes place in private (the accused is not notified) but the Crown is there and asks questions. At this second stage hearing there is a determination if there really is a basis for the prosecution and whether it's in the public interest.
The Crown can step in and stay any criminal charge at any time.
That said, if there is good evidence of, say, an assault the charge will formally go ahead. In that case the accused will be served with the charge by the police and the case will proceed in criminal court.