How good is prohibition?

"A Florida man was jailed for 90 days after cops had suspected he had cocaine in his vehicle, which turned out to be white powdered drywall."

All the initial tests – and a sniffer dog – indicated the white powder all over this black handyman's car was cocaine. Because obviously if you were dealing cocaine you would have it dusted all over the inside of your car. The lab tests – after 90 days of jail – later showed it was plaster residue. 

Prohibition arguably causes more injustice in the world than any other law. How many people has Fentanyl-addict Rodrigo Duterte had gunned down in the Philippines by now?