Records show a Los Angeles police officer shocked a handcuffed woman with a stun gun while joking with fellow officers, in an incident caught on video.
Officer Jorge Santander fired the Taser, proceeding to flash a superman logo he wore on his chest underneath his uniform, the Los Angeles Times reports.
The Times investigation found Santander then appeared to lie about the December 2010 encounter repeatedly in written reports.
The Times found three other officers who witnessed the incident all corroborated Santander's version of events when first questioned. They also failed to tell supervisors that one officer had recorded it on video.
Prosecutors declined to charge Santander.
Police officials say Chief Charlie Beck is seeking to have Santander and the three others fired.
The Times says it is the fourth case made public in the last few months in which LAPD officers are accused of using force on suspects who were restrained.