OK, TV writers. Enough. You’re smarter than this. And the whole game is getting old.

Stop relying on serial killers as plot devices.

Look around. Read the newspapers. Ask Bill Kurtis, for crying out loud. There’s plenty of people committing stupid, heinous murders. Thousands. Every day. Prisons are so full, they kick some of these guys loose early.

So why is every promo for every police drama obsessed with how strange, ingenious and nervy its serial killer du jour is? There’s even a whole series, Showtime’s “Dexter,” whose hero is a serial killer.

Just last week, a commercial for CBS’ “Criminal Minds,” a show still pulling in the ratings, stooped quite low in advertising a fiend who pulled out — and kept — his victims’ eyeballs. There’s even a quick shot of a particularly nasty medical instrument getting ready to harvest a nice, juicy ocular orb.

What is the deal?

Most serial killers are drab, sad doofuses. Why do they get away with their crimes over the years? It’s not that they’re that smart.

I’ll show you: Pick a number between one and a million.

Police find it hard to track these guys without motive or rationale. Such killers are random and insane. That’s why killers grow transfixed with their M.O.’s, weapons and coded notes.

In their minds, this is what substitutes for having actual things to care about. Well, that and they’re about as stable as a meth addict with rabies.

Seriously, though, this stuff is way too easy. Observe:

Cop: “Two more bodies.”

Other cop:“ “Where?”

Cop: ““Stuffed in a mailbox.”

Other cop: ““Tidy. Cause of death?”