HGN is a very reliable and scientifically validated field sobriety test. A properly trained officer will systematically check for three clues of HGN in each of the suspect's eyes. The more impaired the suspect is, the more likely it will be that these clues will be observed. One of several terms used to describe the degradation of driving ability due to alcohol or other drugs. Every state has enacted a version of an Implied Consent law, which serves to encourage persons arrested for DWI to submit to a chemical test to determine blood alcohol content.
Many states also allow for the testing of blood, breath or urine for the presence of drugs.
The concept of implied consent is that the state views the suspect as already having agreed to take the test, as a condition of operating a vehicle in the state. The law further provides that, if the arrestee nevertheless refuses to submit to the chemical test, he or she will not be forced to submit, but the driver's license will be suspended or revoked. At the request of the National Highway Traffic Safety Administration, the Division of State and Provincial Police of the IACP has agreed to develop standards and assist in managing the certification process for the Drug Evaluation and Classification Program. As part of this agreement, the IACP will perform necessary staff and coordination functions for the program. The staff of the Division of State and Provincial Police is responsible for maintaining records for the national program and will coordinate certification and recertification processes.