Plot question about In the Heat of the Night

I’ve got a question about a plot point in the 1967 film In the Heat of the Night.

The movie features Sidney Poitier and Rod Steiger as Virgil Tibbs and Bill Gillespie, a pair of police officers who reluctantly team up to solve a small-town murder. At one point in the film, Tibbs has Sam Wood, the policeman who discovered the body, physically retrace his movements from the night of the murder, minute by minute. Wood drives the other two officers around in his patrol car, at one point passing through a residential neighbourhood. At this point Tibbs deduces that Wood has altered his route and calls him out on it. On the night of the murder, Wood had actually turned down a different street in order to peep at a 16-year-old exhibitionist who customarily stood nude in front of her window, but didn’t want Tibbs to discover this.

My question is, how did Tibbs know that Wood had altered his route? What tipped him off that Wood was trying to hide something?

According to the script I found online (not linking as it’s unlikely to be in the public domain):

Wood “turns the wheel sharply at the intersection just this side of the Purdy house”, and “seems to be sweating more than ever” and then “looks up, into the rear view mirror, seeing Tibbs’ eyes”

I expect we’re supposed to accept Tibbs picks up on subtle cues from carefully observing Wood as well as the route.

I read the book decades ago and don’t remember much but I think Wood hit a pot hole or something that Tibbs thought he would not have hit if he drove the same route he always did.

Sorry if you’re only interested in the movie and not the book.

OK, that makes sense. Probably this is how the scene was indeed filmed, though if so I must have missed the clues when I watched it.

I haven’t read the book but your information is most welcome. The pothole clue seems quite clever so I wonder why that never made it into the screenplay.