In this paper we describe an approach to capture the degree of compliance of a product with an industry standard such as the international standard for functional safety of E/E/PE systems, IEC 61508. We call this the evidential volume of an assessment scenario. It is based on compiling observed evidence according to assigned weighting factors, which describe the relative importance of each piece of evidence. The evidential volume can by itself be used as an indicator to compare different assessment scenarios. This could form the basis for improved consistency in assessment. We suggest a model to relate the evidential volume to the probability of having achieved a product of required safety integrity. Developing such a relationship can lead to a decision-aid on acceptance or rejection or can be used to decide whether additional evidence, such as statistical testing could be used to achieve target safety integrity. The model we suggest is based on the Success Likelihood Index Model (SLIM) and it poses an initial step towards decision-support for assessment. The model developed can be used for any standard, IEC 61508 is used as an example only.