As illegal prescription drug use soars, the number of cases of driving under the influence in which the substance is a prescription drug rather than alcohol is rising steadily, authorities say.
But prosecuting and obtaining convictions against suspects charged with DUI involving prescription drugs can be a challenge.

Many states, including Florida, do not require a test to quantify the amount of drugs in a person's body in a DUI case, and impairment is difficult to prove.

Details.

[Is there a legislative solution? Or do we need to get more blood samples and test for levels as well as identification of the drug? And, then, who is the expert for intoxication?]

The legislative solution is to allow police to obtain a blood sample in all DWI/DUI cases without having to obtain a search warrant. However, even with a blood sample, DPS analysts will tell you that the testimony of the arresting officer is always crucial since there are tolerance issues with most drugs. There is no bright line standard for drugs like that of 0.08 for alcohol.