Regarding the decision process for an interviewer (the decision to move a candidate to second round or to give the candidate an offer) in a case study interview -- Is it solely based on your performance in the interview, or does the firm, in addition to your performance in the interview, also reconsider your performance on the problem test and your CV every time they want to make a decision?
In terms of how interviewers decide, once you are in a consulting case interview, the case performance itself determines 80%+ (maybe 90%+) of the decision. If you're going to get rejected for the McKinsey Problem Solving Test or the consulting resume, that tends to be done early in the process -- either before first round, or during first round.
This is why I place such a strong emphasis on preparing for the case, practicing cases with a friend, or using training tools like my Look Over My Shoulder® Program.
Sometimes you do get a resume-only type interview in later rounds, so maybe six people interview you for final round -- five do case, one might still do a resume. In that case, the resume interviewer is evaluating your answers to his/her resume questions.