I believe a prosecutor does qualify. IRS Pub 575 defines a PSO as including a "law enforcement officer." The Public Safety Officers’ Benefits Act (the law that established the credit), as well as the regs that implement it, include prosecutors in the definition of law enforcement officer. For example, in the Act (42 USC 3769b), the term law enforcement officer means an individual “involved in crime . . . control or reduction, or enforcement of the criminal laws,” and includes "judicial officers.” And in 28 CFR 32.3, “involvement” in crime control or enforcement includes those with authority to “prosecute"; and "law enforcement" includes “prosecution or adjudication.”
Finally, websites from the Nat’l Conference on Public Employee Retirement (NCPERS), the State of Washington, and the County of Los Angeles all adopt this inclusion of prosecutors as PSOs.
