How the umpire checks it
- Start with runners on base. Without runners, there is no balk call.
- Watch for an illegal action such as starting and stopping improperly, failing to step directly toward a base on a pickoff, or simulating part of the delivery without completing it.
- If the illegal motion happens, the umpire marks the balk.
- Then judge the outcome of the live action in codes where play continues: did all runners and the batter-runner safely get at least one base?
- If not, enforce the balk award. If yes, the play result can stand instead.