The Kansas Supreme Court has held that the horizontal gaze nystagmus test (HGN) is not admissible. It was ruled not scientifically reliable This is a test many law enforcement have driver’s perform that checks your eyes for tracking. It is junk science. The Kansas Supreme Court agrees.
http://www.kscourts.org/Cases-and-Opinions/opinions/SupCt/2015/20150130/104940.pdf