So how did the cops figure out it was a setup?
Don’t know. That information seems to be withheld at this point.
But I’d bet the rent, for them to put this out, they have some substantial information in support.
At a guess? Lack of the suspect’s fingerprints on the evidence plus no systemic evidence of drug use (or a recent drug test) by the teacher.
Probably the idiot ex-wife making repeated phone calls accusing the guy of road rage, drug sales and basically turning a fine upstanding citizen into a one-man crime wave overnight.
She should serve some hard time for this.