Generally, the charge of DUI or driving under the influence means the accused is suspected of driving while under the influence of a foreign substance; the foreign substance can be alcohol or another drug. The amount of DUI cases involving prescription drugs has increased as the use of illegal prescription drug has rose. Since many states do not require medical tests to demonstrate the amount of drugs in a person’s body at the time of arrest, proving impairment can be difficult.
Systems to quantify the amount of alcohol in a person’s body are well established, and a well developed system makes it easy to compare the reading of someone’s blood alcohol content to the established legal standard. In many states, there is not a similar standard set for a drug like oxycodone or opiate based drugs. The lack of an ill-defined system can create a difficult evidentiary task for police officers and for state prosecutors.
Officers in the field are usually left with two choices to demonstrate impairment: a measurement of blood alcohol content or the impairment of alcohol or drugs can be demonstrated by the driver. A driver’s demonstration on whether his normal faculties are influenced by a substance is not as clear as a breathalyzer that shows blood alcohol content. In addition to field sobriety tests, some states use police officers who are trained as drug recognition experts.
Even with the variety of methods to measure sobriety, it is still difficult to demonstrate impairment for a drug DUI case because it is hard to prove the amount of drug in an individual’s system at the time of an accident or arrest. To make things more complicated, a person may be taking a legally prescribed drug and the legally prescribed amount may affect different people in different ways.
Source: USA Today, “DUIs Involving Prescription Drugs Difficult to Prove,” Kaustuv Basu, 10/18/10