Noun.
What a person becomes when, upon receiving word of a police incident from
the internet, the news, or word of mouth, one gives advice on how
the police should have "properly" handled the situation in line with police protocol, the law, etc.
Usually, this occurs when
the police have been accused of wrongdoing or, even more commonly, when the police have been accused of no wrongdoing yet the receiving party believes they are almost entirely at fault.
Common occurrences include drug busts, traffic stops, and police shootings.
Theodore: I can't believe the police shot him, he only had a knife on him. Since when do you need to shoot someone
with a knife? They should have used their taser or
pepper spray, it's not even legal to use
deadly force in a situation like that.
Bill: Man, Ted, you are being quite the armchair policeman right now.
Theodore: It's Theodore.
Bill: Whatever, dude.