A Met Police officer made "serious errors of judgment" when she failed to report her sister for sharing an indecent video of a child on WhatsApp, a trial has heard.
Acting Ch Supt Novlett Robyn Williams was allegedly sent a "disturbing" clip of a child engaging in a sex act.
She chose not to tell police through fear it would implicate her sister and her partner, jurors were told.
Ms Williams denies possessing an indecent image of a child.
The 54-year-old from south London also denies corrupt or improper exercise of police powers and privilege.
Ms Williams was one of 17 people sent the video by her sister Jennifer Hodge, who had received it from her partner Dido Massivi in February 2018, the court was told.
Police were alerted by another recipient, rather than Ms Williams, who as a senior police officer had an obligation to report it herself, the jury heard
Prosecutor Richard Wright QC told jurors: "Miss Williams did not report the video. Therefore we say not only did she commit the criminal offence of possessing it, but she also failed to exercise her powers as a police officer to act upon it."
Mr Wright said it was not suggested the defendants had any sexual interest in the video that showed a five-year-old girl engaging in a sex act with a man.
He said: "This is instead a case in which we allege that each of them made serious errors of judgment about how to handle this video and, in dealing with it as they did, each of them has committed serious criminal offences."
Mr Wright said the case was a "sad" one and the defendants are "not bad people".
Social worker Ms Hodge, 56, of Brent in north-west London, denies distributing an indecent image of a child.
Bus driver Mr Massivi, 61, also of Brent, denies two counts of distributing an indecent photograph of a child, and one count of possessing an extreme pornographic image portraying a person having sex with a horse.
The judge, Richard Marks QC, warned the jury that the case involved "pretty unpleasant" images, but told them to "put emotion to one side".
The trial continues.