Loosedhorse
member
I didn't specify car doors in the quote you used. As has already been mentioned, perhaps the most likely aim point at a police car would be the windshield, which is sloped, laminated glass. One would expect at least significant deflection (and maybe defeat of the bullet, depending on the round).A single car door offers NO protection against handgun rounds.
As to the car door test: was the window retracted into the door? Was the door at an angle to the shooter? Were hollow-points (other than .45) used, or calibers below 9mm? What was the gel penetration (standard way we judge wounding potential) of the rounds that got into the interior?
If the tester sets up a worst possible scenario, that can be instructive--and nobody advocates using a car door as chosen cover. As "it happened to be there when the shooting started" cover, it's better than standing out there in the air.
Episodes of handguns fired into police cars are (thankfully) rare. Here's one from NY, 1995:
At the same time, the suspect fired at least 5 shots through the passenger-side open window with a 9 mm semiautomatic handgun. The officers returned fire; however, they did not hit the suspect. Three of the bullets fired by the suspect were embedded in the door on the driver’s side of the police car; one bullet went through the car’s rear left door, and one bullet grazed the bottom metal window rim of the driver’s door and then struck the victim officer in the left torso between his protective vest panels. [emphasis added]
So it seems, at least in this case, 3 rounds that hit the driver's door (from the inside, having been fired through the opposite open window) could not penetrate. Not sure I would rate that as "NO protection."
But your point is taken, and appreciated.