A brutal scene depicting a violent sex attack in BBC One drama Silent Witness is ruled to have broken TV guidelines on offence.
The BBC Trust's editorial standards committee said the "wrong editorial judgment" had been made and the episode was not suitable for its time slot on the channel.
The edition of the crime drama - which stars Emilia Fox as pathologist Dr Nikki Alexander - drew a large number of complaints when it was screened on April 22, 2012 as the programme overran and viewers tuning in for the BBC News At Ten were confronted with the gruesome incident.
A total of 632 complaints were made about the violent content which featured the twitching, moaning body of one character seen in a pool of blood in a toilet cubicle. His attacker was then seen preparing to resume the attack, although the gory detail was not shown.
But viewers were made aware of what had happened when a reference was made to the attack during the programme, the first of a two-part story called Redhill.
In its report, the committee said: "When the prison officer emerged from the toilet holding the bloodied stick with a pool of blood on the toilet floor, viewers were left in no doubt that an act of sexual violence was being carried out. The committee felt that this level of explicitness of sexual violence would have exceeded viewers' expectations of this long-running series.
It went on: "The committee concluded that the final scenes in the toilet block were in breach of the guidelines on harm and offence as they exceeded audience expectations for this series as they depicted a sadistic method of inflicting pain, injury and death.
And the Trust committee said the violent content was "too explicit for this series, on this channel in the first hour after the watershed".