Equipment issues. To any cops reading this, need I say more? For you authors, in your novel, does your main police character ever experience dangerous and often embarrassing moments in the patrol car? These examples came from a friend of mine with somewhere around thirty years of police work under his belt.
“Ever had a cop in a murder mystery where either the radio just wouldn’t work or there was an over-saturation of airtime and he can’t get on the air? I was in a chase once and couldn’t tell anyone. One time I was going Code 3 (lights and siren) while leaning out the window and banging on the light bar to keep it working. Another time a cab driver stopped traffic so I could get out of the 4th Avenue tunnel on a Code 3 run when all my equipment quit. Another time I was about to stop a drug car for MANTIS (Metropolitan Area Narcotics Trafficking Interdiction Squad) and my car died every time I hit the lights.”
If you want realism, write the most ridiculous equipment failure you can think of. I guarantee that some cop somewhere will read it and say, “Hey! That happened to me!”