Not only was she not a sheriff's officer, she wasn't even a man.
Boca Raton police arrested Rachel Lyndsee Otto Tuesday after she -- dressed as a man in military fatigues and wearing a close-cropped hairstyle -- was busted trying to make an arrest while posing as an officer from the Palm Beach County Sheriff's Office.
Otto, the 21-year-old granddaughter of one of NASCAR's first principal owners, Ed Otto, even asked the first community service officer who arrived to send for police backup to help her put away a motorist who had ticked her off on a Florida roadway.
When backup arrived, however, arresting officer Andrew Nguyen recognized the 5 feet, 2 inch Otto, who in 2006 had falsely told him during another police confrontation that she was an employee of the sheriff's office.
Otto, whose family remains active in the sport through its company, Otto Motorsports, has been arrested at least nine times since 2004, according to police.
"From my experience dealing with [Rachel] Otto in September 2006, I know that she was a female and that she was not a [Palm Beach Sheriff's Office] deputy," Nguyen wrote in a probable cause affidavit obtained by ABC News.
Allegedly angered by the aggressive driving of fellow motorist Michael Mellin, Otto first got out of her car at a red light, put on a utility belt she fetched from her trunk and approached his vehicle.
Mellin later told police that he didn't know what was going on, according to the affidavit. When the light turned green, he took off.
Otto then got back into her BMW and after a short car chase, pinned Mellin in with the help of a third motorist who would later tell police he thought he was helping a male sheriff's officer.
This time, Otto ordered Mellin out of the car, demanded his license and handcuffed him -- telling him he was under arrest.
But when Nguyen arrived, he knew better -- and so too, did Otto, apparently realizing she had gone too far.
"I asked Otto what she was doing and she said she was making a citizen's arrest for road rage," Nguyen wrote in his report.
It was too late for Otto, who was arrested for impersonating a law enforcement officer and for false imprisonment of Mellin.
In Otto's car, police discovered a black nylon utility belt that held two sets of handcuffs and a cannister of mace. They also found a woman, who told them that she had moved in with Otto a week earlier and thought she was a man.