For cops, the word "backup" connotes different things. It can mean everything from saving duplicate copies of computer files, to having a secondary firearm, to keeping a street wife on the side. For most, it means having another officer on scene.
But officers like to be prudent in requesting backup. They don't want to impose on other officers. They know their fellow cop is often busy doing his own thing and recognize all too well in a world of constrained resources that time spent on any given enterprise is invariably at the expense of another. They don't want to be seen as incapable of handling their own responsibilities. Most importantly, they don't want to create a reputation as the "boy who cried wolf," where their frequent requests for assistance finds them with no one rolling when they really need help.
As a result, many officers forego requesting backup once a situation is deemed "secure." The suspect has been searched, is in custody, and seemingly cooperative.
But such circumstances are exactly when you might want to have a backup officer on hand, especially in an era where many agencies increasingly field one-person patrol cars.
Having a second officer on scene when things are apparently "code 4" can prevent, or at least mitigate, unfortunate surprises. Little things like having a prisoner slip out of your backseat while your nose is buried beneath the front seat of his POV. Things like the suspect's friends happening along and lynching him from same. Things like fabricated allegations made by the suspect or his friends with no one available to corroborate your version of events.
Such backup can also help prevent escapes, thereby mitigating the possibility of injuries to the suspect or other officers that might otherwise occur in the aftermath of such an eventuality.
Take, for example, the DUI suspect you've placed in your backseat as you're parked roadside waiting for a tow truck. Suddenly, the suspect decides he's not as enamored as you are of the prospect of his wearing your handcuffs. He starts by banging his head on the window, quickly escalating to kicking out the rear window. True, you might have one of those immobilizing contraptions in your patrol car that would prevent this, but humor me on this, particularly as most patrol cars don't have 'em. Do you pepper spray him? Apply a RIPP Hobble Restraint? TASER his uncooperative ass?
Having a second officer on scene automatically gives you more options, not the least of which is having him kick the guy's ass (just kidding). Another officer will not only help you gain control of the man, but give your watch commander a corroborative version of events. It sure as hell is better than arriving back at the station with a beat-to-shit patrol car, or showing up at the local hospital with a suspect whose injuries were sustained after the cuffs were secured, with only your say-so to show for it (another time and place it might have been…but these are risk management times).
If a unit shows himself on a T-stop and you're in the area, take the initiative and roll by just to make sure he or she is OK. Even if they don't need you, odds are they'll appreciate your looking out for them. They might even return the favor.
By having a good working relationship with your sister cars, and being reciprocal in matters of backup, an officer enhances his chances for physical and career survival.