Sure, it's another cop's handle. Yes, you don't want to step on toes, or worse, assume the handle. And no, you don't want to get a rep as a call-jumper.
But more than that, you don't want someone to get hurt—not if you can prevent it.
That's why there are times when you have to speak up and offer some food for thought, especially if the recipient isn't firing on all cylinders. Because of this reality, the following are some things for unassigned units to do when monitoring the radio.
Think About the Implications of a Call
For instance, if the desk sends a one-man car code 3 on a suicide by hanging call, ask them to send two (What's the one-man supposed to do? Hold the hanger up off the ground until someone else just happens along to cut him or her down?).
Once we had a quadruple shooting with two dead and the suspect on foot in the area. The situation was still extremely fluid when the desk advised the following over the coordinating frequency: A man matching the description of the suspect was outside a caller's front door and trying to get in.
I told the desk to have the people inside the house vacate. Doing so not only prevented a potential barricade/hostage situation, but the residents were spared being struck by one of the 15 rounds that were eventually fired by deputy personnel when they engaged the suspect at the front porch (the sixteenth round did the job it was intended to do).
Make the Inferences on Calls Your Dispatchers Can't—or Won't
A call went out as "two prowlers entering the backyard of a residence, followed by the sound of breaking glass." Two one-man cars were dispatched to the call.
That's no prowler call—that's a burglary! was the first thing that came into more than one cop's mind.
Sure enough, upon arriving at the location the handling deputy found a window smashed and an opened door. Fortunately, other units had already taken the initiative and started rolling on his call in the first place, so the suspects were successfully contained inside the location.
Consideration is Important
Like many cops I've known, I'm capable of being a thin-skinned S.O.B. by nature, and resent didactic, dictatorial orders. But I also know that while it's inevitable that we will occasionally step on some toes, people generally take lesser exception if it doesn't hurt them—certain alpha types included. So I learned to tread lightly on the radio while still communicating what needed to be said.
"Have you considered…?" is non-challenging and certainly a fair thing to ask. It can pertain to the handling unit getting an aero unit, a K-9, or having some special logistics rolled from the station. That way if they say they're not interested, at least nobody can accuse you of not trying to help.
Everything isn't an emergency, and unless time is of the essence, be patient. This is particularly true with training cars: Let 'em make mistakes.
Finally, remember that it's difficult for a handling unit to think about every possible need, particularly in a large scale operation. Such times are when you may need to speak up and make suggestions.
Even if you can't be there in person, you can be there for them via the radio.