On the bench

"But serious concerns about whether Kavanaugh lied under oath have also been raised – publicly and privately – on a topic that has received far less attention in the national spotlight: his insistence that he was shocked when he discovered last year that Kozinski, his mentor and friend, sexually harassed more than a dozen clerks in decades on the bench."

(The Guardian.)

Who was "on the bench"? Was it "Kozinski" or "a dozen clerks"?