Eliciting socially optimal rankings from unfair jurors

A jury must provide a ranking of contestants (students applying for scholarships or Ph.D. programs, gymnasts in a competition, etc.). There exists a true ranking which is common knowledge among the jurors, but is not verifiable. The socially optimal rule is that the contestants be ranked according to the true ranking. The jurors are partial and, for example, may have friends (contestants that they would like to benefit) and enemies (contestants that they would like to prejudice). We study necessary and sufficient conditions on the jury under which the socially optimal rule is implementable. These conditions incorporate strong informational requirements, particularly with respect to mechanism designer.