I’ve recently been watching videos of police pulling over speeding cars. It seems that whenever the cop walks to the car for the first time s/he always touches the rear of the car in some fashion. Is this done for a reason?
To show they were at that vehicle in case something happens to them during that particular stop.
Many officers are trained to place a hand on the trunk of the car as they approach, to leave fingerprints as evidence if ambushed by the driver.
It’s really an old school thing that was taught but not really relevant now. On a car stop the officer’s presence is recorded multiple ways for each stop (camera, plate look up, GPS, radio transmissions etc) so it’s not needed. Some are still taught that way and for some it’s just habit. I haven’t done it for 20 years. It probably helped one case one time and spread.
Another reason/superstition floating out there* is that it allows the officer to check the trunk to see that it’s latched, and that there isn’t someone lurking in the trunk waiting for an opportunity to ambush the officer. Which is presumably an idea that predates child safety release handles.
*See, for instance, this article on the Portland police website:
I pull up on the Nissan’s trunk as I pass, to be sure that it is latched and that nobody will pop out of it behind me.
I second Loach on this. I taught my new officers to not do this. It’s a distraction from what the officer should be watching. And I felt it was a form of fatalism, predicting you’ll be killed on this stop and hoping to leave a fingerprint on the killer’s vehicle.
And, along the same lines as Loach said about maybe it helped in one case, there’s a lot of what is actually folklore out there that gets added to pad out material for consultant’s training classes.
In the many times that I’ve been pulled over…
… I don’t recall the officers, both male and female, ever touching my vehicle.
Ever.
I’ll add that my main driving flaw is speeding. On freeways, not in residential areas. And mostly before I realized that my eyesight wasn’t 20/20. Once I got eyeglasses, spotting the Smokeys was easy.
Then you’re not driving fast enough. 
This is exactly what I was going to post.
I first got on the job in 1982. The training then was to leave fingerprints. Then in the 90’s it changed to doing it to make sure the trunk was latched. I don’t know if anyone actually trains either now.
But I do find myself doing it automatically like I’ve done for decades even though I am aware of the release inside. Old habits are hard to break.
Question: What good does it do to leave fingerprints on a car if one of the two things will happen after a cop is killed by the occupant:
- the car will not come under suspicion and it would never occur to cops to dust it for fingerprints,
or
- the car is already on a hot watchlist as a known suspect’s car, in which case the fingerprints are unnecessary, you already know that (license plate XX-XXXX) is the wanted fugitive car?
Huh…I’ve never heard of this - or at least I don’t recall, and it wasn’t a thing among my co-workers. Maybe regional (I was Florida).
Police academy 1977.
Actually, many (most?) officers call in the plate before making the vehicle stop. So that’s a start.
But finding the suspect car is important for identifying the shooter (e.g. through fingerprints or other items found inside). It’s not unusual for someone other than the registered owner to be the shooter. Court convictions require more proof than saying Jones is the registered owner of the car so it must be him.
You should alway check the trunk. The complete Trunk Monkey commercial collection.
This is the worst advice evah!!! Especially if the car is driven by the Repo Man
If I’ve just shot a cop, I’m ditching my license plates and reporting them stolen. Harder to do that with my trunk 
You don’t need to ditch your trunk, you just need to wipe it clean of any fingerprints. Which is even easier than removing your license plate.
See, this is why criminals get caught.
“Why are you cutting the trunk of your car off with an acetylene torch?”
“Fuckin’ fingerprints man!”
“… … Windex exists, you know…”