Benzino -- Claims There Were No Drugs in HIS Car ... Only the Police Car

Benzino's arrest for drug possession had nothing to do with pot being found in his flashy Maserati -- instead, he says the drugs were in the police car in which he got hauled off to jail.

TMZ obtained the police report from his Atlanta arrest, and it says after Benzino was placed in the back of the patrol car ... the police found a small amount of pot on the seat. Cops say the pot wasn't there before.

The officer says he then checked Benzino's waistband and found a small amount of marijuana residue there, and on the fingertips of his right hand.

Benzino and his attorneys released a video (which kinda looks like a hostage situation) ... claiming the weed was in the cop car before he got there -- even though the police report clearly makes it seem like Benzino dumped it from his waistband.

Fun fact: The arresting officer uses a "Gain" laundry detergent air freshener ... which he says wasn't strong enough to mask the pot smell in the back seat.