Determining If a Driver Is Under the Influence

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Determining If a Driver Is Under the InfluenceOperating a motor vehicle while under the influence of alcohol or drugs is illegal. However, in order to charge you, authorities have to gather sufficient evidence to demonstrate to the court that your driving ability was impaired because of a substance in your system. There are different methods for determining whether a driver is under the influence and to what extent. The type of assessment may depend on whether the officer suspects you of drinking alcohol or using some other drug.

Breath Tests

Authorities administer breath tests by asking you to blow into a tube attached to a machine, which then analyzes the alcohol on your breath. This is commensurate with the amount of alcohol in your bloodstream, so taking a breath test allows law enforcement to determine your blood alcohol concentration. Breath tests are increasingly controversial. The criminal justice system relies on them to the point that sometimes the results are the only evidence entered against you in court. However, investigations have discovered that the results of breath tests are not always reliable or accurate due to human errors in calibrating or maintaining the machines.

Blood or Urine Tests

While breath tests are common for detecting drunk drivers, it is not always possible or practical to perform them. Not only that, but breath tests are limited in that they can only detect alcohol. They are useless for finding evidence of the use of other drugs. If breath testing is not feasible for whatever reason, law enforcement may resort to testing of urine or blood. This requires them to collect a sample. The same implied consent laws that apply to breath tests also pertain to other chemical testing. Therefore, there are consequences if you refuse to cooperate.

Field Sobriety Tests

These consist of certain tasks that a law enforcement officer may ask you to perform. He or she gauges your performance to determine if you may be impaired. Field sobriety tests may be effective at detecting drivers who are drunk and/or drugged. However, even the most effective of these is only successful about 70% to 90% of the time.

Three field sobriety tests have been researched and shown to be the most successful at identifying driver impairment. These are known collectively as standardized field sobriety tests. However, authorities are not required to use these tests. They are allowed to use non-standardized field sobriety tests if they choose. However, the results may not be admissible in court.

If you are accused of driving under the influence, a drug possession lawyer in Bloomington, Illinois may be able to assist you with your case. Contact a law office for more information.


Thanks to Pioletti, Pioletti & Nichols for their insight into criminal law and determining if drivers are under the influence.