Why did the kidnappers let the cops know that it was a kidnapping?

SPOILER

It seems that Charnier's plan was to get Doyle addicted to dope, and then the cops would think he became a drug addict and that he would be a disgrace. Is this right?

But the kidnappers decide to dump him right in front of the cops, by shoving him out of a car. This raises a lot of suspicions on the kidnappers, because now there are several eyewitness officers who saw them, and the make of the car, possibly with a license plate.

Wouldn't it make more sense to dump Doyle off in a place where there was no witnesses?