A lot of speculation here

so let's add a touch more.

According to this NYT article, the Justice Department has declined to prosecute any C.I.A. officers in the deaths of four prisoners in Iraq and Afghanistan. They will bring charges against one contract employee, however. What conclusion does the reporter draw from these facts?

...the prosecutors' decisions appear to reflect judgments that the C.I.A. was far less culpable in the mistreatment of prisoners than was the military, where dozens of soldiers have been convicted or accepted administrative punishment for their actions in cases in Iraq and Afghanistan.

Let me add a different one, one perhaps more supported by the few facts presented in this article.

Fact 1:

All of the cases have been reviewed by the C.I.A. inspector general, and in at least two of the cases - the deaths at the Salt Pit and Abu Ghraib - the individuals could still face punishment by internal accountability review boards, which could be convened at the discretion of Porter J. Goss, director of the agency.

Fact 2:

C.I.A. officials have expressed deep unease over the possibility that career officers could be prosecuted or punished administratively for their conduct during interrogations and detentions of terrorism suspects.

Fact 3:

The details remain classified, and the current and former law enforcement and intelligence officials who described the status of the cases declined to discuss them in detail. The officials came from several intelligence, law enforcement and military agencies.

Every schoolchild knows that espionage cases are hard to prosecute, because they involve "national security issues." John Dean has even speculated that "national security" could be the "get out of jail free card" in the Plame investigation. Why would the DOJ want to penetrate national security and the classified status of agents (some of whom, presumably, are, like Valerie Plame, "undercover"), for the sake of a few convictions regarding the deaths of foreign nationals in the two countries we invaded?

It's almost a no-brainer why the CIA officers involved won't be prosecuted. It may not simply be for lack of evidence of culpability.