Sam Lutfi -- Pants on Fire Over Britney Spears Head-Shaving

Sam Lutfi lies ... because we have video of the man going after Britney Spears' family in court ... saying THE OPPOSITE of what his lawyer claimed in court -- that Britney shaved her head while in a paranoid, drug-fueled state.

TMZ shot video of Lutfi back in 2010, and we asked him about the incident. Sam NEVER said anything about drugs. To the contrary, he told our photog he thought Britney shaving her head was "a cool thing ... somebody expressing their artistic side."

Lutfi went on ... "I think she was just expressing her independence and her freedom ... there's nothing wrong with Britney. She's awesome."