"San Diego cop claimed he accidentally locked himself in" #238
Extremely plausible.
Passenger car based police vehicles as that depicted in #238 graphic are often modified for carrying restrained suspects.
Those modifications frequently include a taxi style barrier between front seat-back and ceiling (depicted at link),
to prevent drunken suspects while handcuffed in the back seat from kicking policemen in the front seat in the head.
It's also quite common for the back seat interior door-handles to be removed, so subjects can't open the door and escape.
The back doors of such vehicle may otherwise operate normally, but only from the outside, by obvious conventional means.
This "San Diego cop" may be evil incarnate, or the second most saintly human ever born.
The above quotation provides no insight to where this "San Diego cop" resides on that spectrum.
It may have been as innocent as COP trying to apply automobile lap / shoulder restraint for transport.
In an emergency a COP thus trapped in his own vehicle could use his sidearm to hammer or shoot out
the rear door glass, reach through the open window, and open the back car door from the outside door handle.
But that would required some 'splainin' to his chain of command, an explanation he's likely to have been eager to not to have to provide.