looking over shoulder
look over (one's) shoulder
1. To be vigilant for some danger or harm that one suspects or fears they may encounter. Likened to literally looking over one's shoulder to see what is behind or following them. He may have escaped the police for now, but he'll be looking over his shoulder for the rest of his life.
2. To monitor one's actions, activities, or behavior to ensure it is correct or following a prescribed standard. Major corporations are opposing the legislation, wary of having the government constantly looking over their shoulder.
looking over one's shoulder
Fig. keeping watch for danger or threats to oneself. Bob's a little paranoid. He's always looking over his shoulder.