Flanagan has twice requested a dismissal of the case, saying that Spears should be allowed to pay a $10 fine and not face a criminal trial.
The 26-year-old singer is scheduled to go on trial in October on a single misdemeanor charge that she did not have a valid California license when she hit a parked car in August 2007 and left the scene.
Flanagan also argues in Monday's filings that Spears is unable to meaningfully participate in her defense because of her conservatorship. Since February, her father has controlled the singer's personal and financial affairs.
Also Monday, the pop star told a New York radio station that her clip "Piece of Me" leaves room for improvement - despite winning three MTV Video Music Awards earlier this month.
"It's a cool video, but I think by far I've done videos that are way better," the singer said in an interview with top 40 radio station Z100. "So I was really shocked that ... it got the award."
Spears called her triple victory "inspiring, though, because now going forward with the videos that I'm doing now, I can really go there and do something crazy and see what happens."
Spears, whose new album "Circus" drops Dec. 2, plans a possible world tour next year.
