A senior Justice Department official said Holder envisions a probe that would be 'narrow' in scope, focusing on 'whether people went beyond the techniques that were authorized' in Bush administration memos that liberally interpreted anti-torture laws. Current and former CIA and Justice Department officials who have first-hand knowledge of the interrogation files contend that criminal convictions will be difficult to obtain because the quality of evidence is poor and the legal underpinnings have never been tested. Some cases have not been disclosed, including an instance in which a CIA operative brought a gun into the interrogation booth to force a detainee to talk. Other potentially criminal abuses have come to light, including the water-boarding of prisoners in excess of Justice Department guidelines, and the deaths of detainees in CIA custody in Iraq and Afghanistan in 2002 and 2003. Opening a criminal probe is something Holder 'has come reluctantly to consider,' the Justice Department official said, stressing that he has not reached a final decision. 'But as attorney general, he has the obligation to follow the law,' the official said. Others familiar with Holder's thinking say that such an investigation seems all but certain, and that a prosecutor probably will be selected from a short list Holder asked subordinates to assemble. Such a prosecutor would examine cases that are generally at least five years old, and probably some that were reviewed previously by career prosecutors who concluded that they could not be pursued. 'I don't blame them for wanting to look into it,' said a former high-ranking Justice Department official familiar with the details of the program. 'But if they appoint a special prosecutor, it would ultimately be unsuccessful, and it would go on forever and cause enormous collateral damage on the way to getting that unsuccessful result.' Bracing for the worst, a small number of CIA officials have put off plans to retire or leave the agency so that they can maintain their access to classified files and be in better position to defend against a Justice Department probe. 'Once you're out it gets a lot harder,' said a retired CIA official who said he had spoken recently with former colleagues. The investigation probably also would target private contractors who worked for the CIA during the interrogations. Current and former U.S. officials interviewed for this story spoke on condition of anonymity because of the secrecy that still surrounds Holder's deliberations and the details of the interrogation files. President Barack Obama repeatedly has expressed reluctance to launch a criminal investigation of the interrogation program, but has left room for prosecution of individuals who may have broken the law. Obama and Holder have said they believe water-boarding constituted torture. An investigation would pose thorny political problems for the administration, and probably draw criticism over questions of fairness. 'An investigation that focuses only on low-ranking operators would be, I think, worse than doing nothing at all,' said Tom Malinowski, advocacy director for Human Rights Watch. A probe also probably would drive a new wedge between the CIA and the Justice Department, agencies with a fractious history that have struggled to work more closely together since the Sept. 11 attacks. Holder's interest in appointing a prosecutor to mount an investigation reportedly surged after he recently read a still-classified 2004 report by the CIA's inspector general citing extensive problems and abuses in the agency's interrogation program. The bulk of the report is expected to be released later this month. Former CIA officials said the most disturbing section deals with water-boarding, a technique in which prisoners are made to feel they are drowning. The Justice Department authorized water-boarding in an August 2002, memo that contained a caveat that could prove critical to any criminal probe. While allowing the approved methods to be 'used more than once,' the memo stipulated that 'repetition will not be substantial because the techniques generally lose their effectiveness after several repetitions.' One passage of the CIA report declassified earlier this year said the method had been used 'at least 83 times during August 2002' on Abu Zubaydah, the first senior al-Qaida figure captured by the agency. The water-board was then employed '183 times during March 2002' on Khalid Sheikh Mohammed, the alleged mastermind of the Sept. 11 attacks. The inspector general also voiced alarm over how much water was being used. Rather than dripping liquid from a canteen, as the 2002 memo envisioned, CIA interrogators 'applied large volumes of water,' raising questions about whether the method 'was either efficacious or medically safe.' Because of such documented discrepancies Justice Department officials and legal experts regard the water-boarding abuses as cases that hold the most promise for prosecution. Even so, the cases are hampered by legal and logistical complications. The U.S. anti-torture statute requires proving that an individual 'specifically intended to inflict severe physical or mental pain or suffering,' a daunting legal threshold. Beyond that, officials said it's not clear that any CIA interrogators were ever informed of the limits laid out in the Justice Department memo. 'A number of people could say honestly, correctly, `I didn't know what was in it,'' said a former senior U.S. intelligence official familiar with the inner workings of the interrogation program. The CIA report also cites cases in which interrogators engaged in potentially illegal improvisations. One interrogator brandished a gun, former CIA officials said. Other prisoners reportedly were threatened with bodily harm, including being buried alive. Agency spokesman Paul Gimigliano said the CIA cooperated extensively in 'referring actions for potential prosecution, and in dealing with career prosecutors who decided if and when specific cases would be pursued in court.' To date, only one case has been. In 2007, a CIA paramilitary contractor, David A. Passaro, was sentenced to eight years in prison after being convicted of using a flashlight to beat an Afghan detainee who later died. In addition to the sweeping 2004 document, former CIA Inspector General John L. Helgerson, who recently retired, also produced a dozen or more follow-on reports that could motivate the Justice Department probe. Among them are examinations of other cases that involved the deaths of prisoners in agency custody. In 2002, an Afghan prisoner died of hypothermia after being stripped, doused with water and left overnight in a frigid CIA lock-up near Kabul, the Afghani capital. One CIA officer faced internal sanctions over the episode, but the undercover operative in charge of the facility later was promoted to be chief of station in Baghdad, former CIA officials said. A year later, an Iraqi prisoner died of asphyxiation after being captured in a violent raid by Navy SEALS and then having his arms chained behind his back in a CIA interrogation cell at the notorious Abu Ghraib prison. The leader of the SEAL team was later acquitted of criminal charges. The CIA interrogator, Mark Swanner, has not faced prosecution. The two cases are believed to have been among 19 examined by a special Justice Department task force set up in Alexandria, Va., in 2004 to investigate CIA abuses. The panel did not investigate the use of water-boarding. Former Justice Department officials familiar with the effort said that 17 of the cases were rejected by mid-2006. It is not clear what became of the other two. Official cited a host of problems, including difficulty locating witnesses and identifying documents -- such as clinical examinations or autopsies -- that could withstand scrutiny in federal court. 'We wanted to make these cases,' said a former Justice Department official familiar with the matter. 'We looked at them as hard as we could and they just weren't there. They weren't there because of the way they were investigated, because of the facts, because of the lack of witnesses and evidence.' 