Common Cause lists these as issues that need to be investigated and calls for a special prosecutor to be appointed:

* Warrantless spying on Americans.
* Misuse of the state secrets doctrine.
* Preventive detention and secret prisons.
* Use of torture and other interrogation abuses.
* Deliberate flaunting of Congress' oversight role.
* Politicization of the Justice Department.
* Abuse of executive privilege.
* Misuse of signing statements to override laws duly passed by Congress.

That seems to me more than sufficient to mandate an investigation. But I would add one glaring omission:

* Presenting false evidence and lying to Congress and to the American people, as well as the United Nations, as justification for invading Iraq, a sovereign nation which was no imminent threat to the United States.

Ralph