Even before its report was final, Gibson, Dunn & Crutcher’s probe of Gov. Chris Christie’s possible role in the Bridgegate scandal had been called into question by New Jersey politicians and other critics for its presumed bias.

The New York firm was after all hired by Christie to conduct the internal investigation as a preemptive strike. And the probe is headed by Gibson Dunn partner Randy Mastro, who twice worked for Christie ally Rudy Giuliani in New York—as an assistant federal prosecutor and then as deputy mayor.