Establish Your Identity interrogation techniques
Establish your Identity techniques are a family of methods for obtaining information from subjects of interrogation. When they work, they result in the subject eagerly offering information. Their use tends to be limited to strategic or long-term interrogation, as they can require an enormous amount of work on the part of interrogators and support personnel. The interrogation team must construct an identity of a person, who would be in very serious difficulty if captured, an identity that the prisoner very much does not want to have.
If the prisoner is, in fact, a serious adversary with little hope of a good outcome, the technique is moot. When Heinrich Himmler, head of the Nazi SS was captured, he tried to convince his captors that he was a minor private soldier; there could be no worse outcome than being identified as who he was.
It is most effective when the prisoner is a mid-to-low-level part of a large organization; it is less effective with small non-national groups, but still can be a concern. A 1978 U.S. Army manual spoke of it being useful, during the Vietnam War, with captured insurgents who could be accused of being a senior Viet Cong officer wanted for serious offenses. For the method to be practical, the interrogators had to have plausible narratives or documents that could reasonably suggest that their prisoner is someone else. These need considerable effort to construct, especially if they employ File and Dossier interrogation techniques needing the preparation of volumes of documents, or the We Know All interrogation techniques that require the interrogators to have a very plausible story. As described in the guidance document, an "interrogator insists that the source has been identified as an infamous criminal wanted by higher authorities on very serious charges, and he has finally been caught posing as someone else. In order to clear himself of these allegations, the source will usually have to supply detailed information on his unit to establish or substantiate his true identity. The interrogator should initially refuse to believe the source and insist that he is the criminal wanted by the ambiguous "higher authorities." This will force the source to give even more detailed information about his unit in order to convince the interrogator that he is indeed who he says he is.""
In Afghanistan, all of Mackay's prisoners were members of irregular units, so it was possible to use many variants. Accusing one of being a civilian-clothed spy, subject to summary execution, could be quite plausible. 
Both in Afghanistan and Iraq, there was the reverse problem: the interrogators truly believe that their prisoner is significant, but, in some cases, the prisoner was actually a low-level participant or even bystander, of a low enough actual status that his real identity might not be believed.
Guantamo guidance mentions this established technique only briefly. 
The goal is to induce the futility associated with the prisoner's ceasing of resistance, and the start of cooperation.
- Jennifer K. Elsea (September 8, 2004), Lawfulness of Interrogation Techniques under the Geneva Conventions, Congressional Research Service, CRS Order Code RL32567
- , Appendix H: Approaches, Field Manual (FM) 34-52: Intelligence Interrogation, U.S. Army, 8 May 1987
- Chris Mackey & Greg Miller (2004), The Interrogators: inside the secret war against al Qaeda, Little, Brown & Co., ISBN 0-316-87112-5, p. 480
- Jerald Phifer (October 11, 2002), Memorandum for Commander, Joint Task Force 170: Request for Counter-Resistance Strategies, Joint Task Force 170, Department of Defense