The standard dialogue from the US on prisoner abuse is that it is not condoned, and that when it is discovered, the perpetrators are punished.
Daniel Johnson was a civilian contractor at Abu Ghraib, working as an interrogator for CACI International. Sometime in late November 2004 (the exact dates are fuzzy), he interrogated an Iraqi policeman who was suspected of smuggling a gun into the prison. He was assisted in these interrogations by a Titan Corp translator, Etaf Mheisen, and two military police whose names may be familiar - Ivan Frederick II and Charles Graner. During these interrogations, according to Frederick,
Johnson told him to cover a prisoner's mouth and nose to stop his breathing. The former military policeman at Abu Ghraib said that Johnson had also instructed him to inflict pain by squeezing pressure points on the same prisoner's face and body. Graner, who received immunity from further prosecution for his cooperation with Army investigators, said that he also "roughed up" this prisoner at Johnson's instigation.
So they smothered and choked the guy and basically beat him up in order to get him to talk - a clear case of (crude) torture, and a clear violation of both US and international law. The US Army investigators recognised this, and passed the case to the US Department of Justice for further action (the Justice Department having jurisdiction over contractors). The Justice Department refused to prosecute, citing "insufficient evidence". Which begs the question: how much evidence do they need? Here, they have eyewitnesses willing to testify, and photographs of Johnson placing the prisoner in "an unauthorised stress position". People have been convicted and even sentenced to death on far less.
There's a clear parallel with the case of Mark Swanner, who tortured a man to death in Abu Ghraib, but has likewise escaped prosecution. And with Chief Warrant Officer Lewis Welshofer Jr, who asphyxiated an Iraqi General during interrogation. But Welshofer at least was prosecuted, even if the jury then gave him only a slap on the wrist for smothering a man to death. Johnson and Summers aren't even getting that. And even clearer than the punishment in the Welshofer case, this sends the message that torture is acceptable, and that the US government will not hold people accountable for it.
So much for "punishing the perpetrators"...