Alright, first a disclaimer: While I have no direct evidence that Mischa Barton is in fact smoking pot, that is what it looks like. Call me crazy, but in Hollywood, when you see someone smoking a hand-rolled cigarette, it's usually not a herbal cigarette. Unless you mean "The Herb."
Now, I'm not going to get on a soap box regarding my own personal thoughts on drug use, but if you are going to smoke a joint, can you not smoke it in the car, and specifically, in the driver's seat?
Like I said, we can't know for sure that Mischa Barton is smoking marijuana, but she could at least take some pointers from Paris Hilton, and let someone else drive.
Photo credit: Flynet