There is a large body of evidence on the efficacy of the cognitive interview. A good place to start is with Milne & Bull's 1999 book, Investigative Interviewing.

For eyewitness testimony, take a look at Elizabeth Loftus's 1996 classic text.

Papers on the developing application of the original technique to consent can be found here, for example:

Suzanne Conboy-Hill, Val Hall, and Dave Taylor 2012. ‘Virtual worlds, people with learning disabilities, and capacity to consent: a feasibility study’. Clinical Psychology Forum, July 2012, pp 23-27.

Conboy-Hill, S. 2006 'Vulnerable Adults; assessing capacity to consent.'  Clinical Psychology Forum, 158  19-23 

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