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