Justin Bieber may insist that he wasn't behind the wheel of his Ferrari when he was speeding like a bat out of hell in his Calabasas, Calif. neighborhood -- and rapper Tyler the Creator may corroborate that -- but the cops don't believe him.

TMZ reports that despite Tyler (of rap group Odd Future) taking the heat for driving Bieber's whip on Memorial Day, several eyewitnesses say that they saw Bieber behind the wheel, including one neighbor who, for whatever reason, thought he'd be able to chase a speeding Ferrari down on foot ... in socks.

Bieber's team insists they have security camera footage showing that he wasn't driving at the time of the incident, but the sheriff's department isn't buying it -- and the footage has yet to be turned over.

To clear his head and make the pain go away, Bieber's been partying pretty hard. Though he's still a baby (baby, baby, oh) in terms of legally drinking in the US, that hasn't stopped him from partaking in partying with lots of older chicks.

Radar Online reports that the 19-year-old Biebs thoroughly enjoyed a stint in Miami full of booze, strippers and bad influences. Witnesses insist he wore sunglasses the entire time. At night. While he was inside.

Sources say he went club-hopping in the steamy city on Sunday night, hanging out with go-go dancers and capping off his night at a strip joint. The singer did more of the same on Monday, except instead of strippers, he was accompanied by a group of 20-something ladies, who later joined his three-SUV caravan back to the hotel room he was sharing with Lil Twist.

We're sure everything ended really well. And if not, it doesn't matter -- he's got confidentiality agreements to back him up.