This could still work with a 3I Holmes, because Holmes himself was a freethinker, with his deductions based upon his intimate observation knowledge of the culture in question. In the 3I, he could have encyclopedic knowledge of all the major (and most of the minor) cultures in his area of operations. Once he knew with which culture his sucpect self-identified, he could apply his deductive technique. Dramatic conflict could come in when either Holmes was unfamiliar with the particular culture (rare) or couldn't figure out which applied (even rarer).