That's the conclusion of a months-long investigation by the county inspector general's office.
According to the report, while FitzGerald was often driven by staff to county events, he says he sometimes drove himself early in his term.
FitzGerald's license expired in the early 2000s, and though he held a temporary permit for several years, he didn't get a valid, permanent ID until 2012.
The 45-page report calls FitzGerald's driving without a valid license a "breach of the public trust," and says he should face discipline.
But the inspector general's report also notes the only people with the power to discipline the county executive are the county HR director -- and the county executive himself.
FitzGerald answered questions about the report in an interview about his campaign for governor on 90.3's The Sound of Ideas.
"It certainly was a mistake to let my driver's license expire, and people should make their own decision about how important that is to them," FitzGerald said, referring to voters in the governor's race. "It's an expired driver's license, and that's what it is. And I don't make any excuses about it."
He said he didn't believe driving without a valid license affected the job he's done as county executive.