Lindsay Lohan's Assistant Ratted Her Out to Cops -- Lindsay WAS Driving!!!

Lindsay Lohan's assistant rolled on her when he spoke to cops after her car accident on Pacific Coast Highway last June, and that's a big reason why she will be prosecuted ... TMZ has learned.

Cops interviewed Lindsay's assistant Gavin shortly after the crash -- at the hospital where Lindsay was being treated -- and according to law enforcement sources, he told police he was riding shotgun when the accident occurred ... and Lindsay was driving.

As you know, Lindsay told cops she was a passenger in her Porsche, but authorities don't believe her and she will be charged with the crime of lying to cops.