College replay rules/ requirements

[chas]

can someone tell me what the rules are for overturning/upholding a call on the field in college. A few weeks ago I saw some calls in the Iowa- Indiana game that went to replay and the replay decisions were strange at best. Same goes for the Illinois- fresno st. game today. 2 point try by Fresno has a pass hit the receiver then the ball is knocked out of the receiver's hands by the defender , the ball caroms backwards and a Fresno lineman catches it and proceeds into the endzone. call on field is that the defender hit the ball thus making reception by lineman legit. It went to replay and as far as I could see the ball clearly hit the receiver first, then the defender then the lineman, making, according to the announcers, a no catch. Replay confirmed call on the field. Does replay guy have some sort of parameter he has to follow to overturn call on field? Are replay guys officials?