There's not much data involved - your vote and a writeup of your impressions are all you contribute. You get the guy's resume prior to the interview. The hiring manager will assign areas of coverage prior to the in-person interviews. There is a set of core qualities in a potential hire that are enumerated in policy and looked for.

It does happen that all but one will be positive on someone and the naysayer will make some points about shortcomings he spotted and others will realize that they were seeing clues to this gap at the time but did not recognize it.

I've never seen multiple negatives won over though.

I reckon I devote 2-8 hours a week to hiring, but since last September I've only participated in extending 2 offers.