If you’re writing “on spec” you should arrive at court early and approach the Clerk of the Court and explain what you’re doing. Also introduce yourself to the police prosecutor.
The etiquette is to be polite, ask questions, sit where you’re told to sit, and ask more questions so there’s no possibility of you getting facts wrong. Learning how to write court reports so an editor feels confident probably requires doing a course. I can’t explain it all here, there’s just so much to know. If you’re worried, take your article to the Clerk and see if they think it is okay.