The Illinios Supreme Court remanded a case to the trial Court to determine the scientific reliability of the Horizontal Gase Nystagmus Test or HGN test.  The HGN test pretends to determine the level of alcohol in a person's system based on a jerking of the eyes.  However, there are over 43 different factors in addition to alcohol that can cause the eyes to jerk.  The ruling puts Illinois on a short list of states where the scientific admissibility of HGN tests for purposes of court evidence in DUI prosecutions is undecided. A 2002 federal court opinion recorded that 43 states have ruled on the admissibility of HGN tests.  They are not admissible in three states including Kansas, Mississippi and Pennsylvania. In most  state including in Georgia, courts have decided that the results of HGN tests are admissible in evidence in a DUI trial.

The National Highway Traffic Safety Administration Standardized Field Sobriety Training Manual says HGN tests have a 77% reliability rate in positively identifying drivers potentially impaired by alcohol, making such tests the most reliable roadside evaluations for impairment.  The "walk the line" test and "one leg stand" test are 65% and 68% reliable respectively.  Meaning that these "field evaluations" are not much better than a coin toss.  

Circumstances from head trauma to flashing lights to nicotine to motion sickness can result eye jerking during HGN DUI testing.  On September 20, 2007 the Illinios Supreme Court wrote  that “HGN testing appears to have as many critics as it does champions.”   The Court reversed and remaned the case back to a Peoria County trial court to determine the accuaracy of the test. The Supreme Court reasoned that the accuracy of HGN tests is sufficiently in dispute that the trial court must hold a hearing to determine whether the tests are scientifically valid, something that has never been done in Illinois.  The last hearing to determine the reliability of the HGN test was held in Washington State in 2000.   The Illinios high court decision was unanimous. 

The HGN tests are favorites for Georgia DUI officers especially Atlanta DUI Officers and Henry DUI Officers.   Some Georgia State Patrol DUI offiicers claim they can tell if you DUI based on HGN alone.  However, what may work in the quite darkness of a doctors' office is not necessarily accurate in the field on the side of a busy highway with strobe lights flashing everywhere.  

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