As part of the CREDO project, UNHCR published an extensive report on credibility assessment in EU asylum systems. The report also covers the use of COI for assessing credibility of statements of asylum seekers.
The report “Beyond Proof – Credibility Assessment in EU Asylum Systems” was publishd as part of the project Towards Improved Asylum Decision-Making in the EU (also called CREDO project) and aims to
“…contribute to the further harmonization of Member State practices as they relate to the assessment of credibility. This report seeks to clarify some key concepts, reference key standards, outline factors that have a bearing on the credibility assessment, and provide some insights into state practices on specific aspects of the credibility assessment. …There is a pressing need for comprehensive and up-to-date guidance on credibility assessment to address the challenges faced by adjudicators in asylum systems. UNHCR has therefore embarked on the review of its own guidance with a view to producing updated guidelines on credibility assessment that reflect recent developments in international refugee law and other relevant areas of law. This report thus does not constitute that updated guidance, although its findings will be taken into account in the guidance’s preparation process.” (via Forced Migration Current Awareness Blog)
Regarding the use of COI, see chapters 4.4.1. (on gathering COI, p. 128-130) and 5.4. (consistency of the applicant’s statements with COI, p. 173-175).