Dr. Bart Kepple and Lt. Columbo in “Unfinished Business”

In that case I'm deeply grateful for one thing.

Lt. Columbo

What's that, Doctor?

That you've established that White was killed between 7:30 and 8 because you and I have been together constantly since 7:30, starting in the cutting room and ending, I hope, now. Otherwise I'm positive you'd still be accusing me.

Lt. Columbo

Well, Doctor, I've never accused you of anything.

I'll ignore that because I'm convinced that my only real protection in this matter is the fact that you personally are my alibi.

Lt. Columbo

And that's a tough nut to crack.

That's not tough. That's impossible.