Prosecuting a DUI case based on drugs can be much more difficult for the State to prove than a DUI based on alcohol use if the driver refuses to take chemical tests.
The law states that if a person has any amount of drugs in their system while driving they are guilty of dui. But if the driver refuses to take a chemical test, the state must prove that he or she was under the influence of drugs. This can prove to be difficult because if the state intents to elicit an opinion from the arresting officer that the driver was under the influence of drugs, the officer must be properly qualified to give such an opinion. That means that they must have significant narcotics experience and training. Many traffic cops do not have such experience so their opinion cannot be admitted at trial.
Without chemical tests and an opinion from the officer, their is usually not enough evidence to prove a person guilty beyond a reasonable doubt of driving under the influence of drugs.
Author: Dennis Dwyer