Carnage Matey! is spot on (again). I've seen a number of CR exercises by companies. A common method is to use an objective scoring system based criteria that can count for or against you with a weighting attached to each criteria. Obvious examples for BA would be disciplinary record, absenteeism, and grading at last performance review (not sure how they work at BA).
A system based on LIFO or seniority is not going to happen.