- What makes you so sure?
- Why do you doubt it?

3 seconds sound clip from the In the Heat of the Night (1967) movie soundboard.

You can hear this line at 01:34:12.628 in the Blu-ray version of the movie.

Quote context

[...]

- I was hung up trying to get Endicott for personal reasons.

- Do you know what I'm gonna do, Virgil? I'm gonna take you over to Brownsville and put you on the bus myself!

- You aren't taking me anywhere, you dig?

- You're holding the wrong man!

- What do you mean I'm holding the wrong man? I got the motive, which is money, and the body, which is dead!

- What makes you so sure?

- Why do you doubt it?

- Because Colbert was killed here, then driven back to town in his own car and dumped on the streets.

- Sam couldn't have driven two cars.

- What do you want?

- Give me till morning.

- You know, Virgil, you are among the chosen few.

- How's that?

- Well, I think that you're the first human being that's ever been in here.

[...]