Decisions about the significance of an association or an exclusion based upon trace evidence require an evaluation of debris in its context; reference points for such evaluation are presented. Samples of debris from the sites relevant to the event under investigation must be available, as well as debris standards from the usual environments of the people involved. The samples must be of an amount and quality that permit a determination of normal versus foreign debris. The author proposes criteria for establishing contact based upon corresponding sets of particles and fibers, for excluding contact in the absence of corresponding particles or fibers, and for refraining from making either an association or an exclusion. Conditions for reaching qualified conclusions or other types of associations when these criteria are only partially met are also discussed; conclusions may sometimes be reached if potential sources for debris particles and fibers can be found. Decisions about the strength of an association or an exclusion based on comparisons of non-component debris particles and fibers can be made by reference to the criteria for reaching a conclusion. The criteria can be tested via Bayes' Theorem. The analysis itself is based primarily on light microscopy, although other methods may be used as well. Ten case examples are presented. 85 references