Fourth Amendment? What Fourth Amendment?

Decision of the Day has this summary of a distressing case from the 8th Circuit. The relevant facts:

as part of its drug enforcement efforts, the Sheriff’s Office of Dallas County, Iowa, posted signs along the highway informing drivers that there was a drug checkpoint ahead. Of course, any such checkpoint would be patently unconstitutional. No such problem here, however, because there was never any checkpoint. Instead, the signs were a decoy to trick drivers who were transporting drugs into using the next exit to get off the highway. Officers with drug-sniffing dogs were stationed at that exit ramp to observe any traffic violations that could justify a stop and search of exiting vehicles.

Defendant Obed Rodriguez-Lopez apparently fell for the ploy and exited the highway at the monitored ramp. He failed to use his turn signal at the stop sign, so officers pulled him over. A drug-sniffing dog alerted, and officers found marijuana. In his subsequent trial, the defendant moved to suppress the marijuana on the ground that the stop of his vehicle was unconstitutional. The district court denied his motion to suppress, and the defendant was convicted.

The Eighth Circuit affirmed, sadly. There is only one job I can think of where the courts encourage you to lie to people: police officer.