Police Officer Preparation & Law Enforcement Resource - Archive

I'm writing a book, and even though some of it is not the real police world, since it has be to fictionalized, I would like to make it as real as I can outside the fictitious parts, especially since it's a very dark story, and I wanna be respectful to as much of the reality, as I can therefore. Now the ranks are different in every county and jurisdiction of course.

Here's the real ranks I looked up, in the areas I will probably end up setting it.

Sergeant, Lieutenant, Captain, Commander, Inspector,

Chief Inspector, Deputy Director, Director General of the SQ

Now out of all these ranks there are 3 main police characters I will need to perform certain duties of the plot. Witness Protection. I know the police normally does not do witness protection, but in my case, it's a dangerous emergency, and everyone is shorthanded, so the cops are forced to lend one of their officers out as a helping hand. Which ranking officer would be the one?

And there's the high ranking officer that runs the precinct he works in, decides what's what, but more importantly handles the press, and gives advice to the public through the media. Who would do that more likely?

Then there is a lower ranking decision maker who takes orders from that superior officer in charge and passes it along to the lower ranks, but still has high influence with the superiors decisions and what not. Would this fit any bills?

Thanks for the input.