How can I be charged with a DUI when I was not high while driving?

Per Se DUI Laws

Pennsylvania’s DUI law prohibits a person from driving, operating, or being in actual physical control of a motor vehicle with any amount of a Schedule I, II, or III controlled substance or a metabolite of such substance in his or her blood. While the DUI law prohibits a person from having “any amount” of a controlled substance in the blood, the Department of Health is actually required to prescribe minimum levels of controlled substances that must be found in the blood for the test results to be admissible in a DUI prosecution. The minimum levels of controlled substances required to justify a DUI prosecution are set relatively low so even minor use of drugs can lead to DUI charges.

Everyone knows that the body processes alcohol, often at a rate of one drink per hour.  The alcohol and its byproducts are eliminated from the body through urine.  With drugs, the body also processes the substances, but the residue or byproducts often remain in a person’s system for days, weeks, and possibly even months after use has stopped.  This means that a positive drug test may evidence drug use that occurred days prior to the test, so the person may not be under the influence or actually high when driving, but the person can still be arrested and charged with driving under the influence.  Under the per se drug DUI law in Pennsylvania, a person can be prosecuted for DUI if he or she has an amount of controlled substance in his or her blood that exceeds the minimum levels established by the Department of Health even if the person was not under the influence of the drug while driving or operating his or her vehicle.

Legalized Marijuana Use

The fact that many states allow people to lawfully use marijuana means that some per se DUI laws are probably unconstitutional.  It seems like common sense that a state cannot allow a person to use marijuana for medicinal or recreational purposes but then prevent that person from driving with metabolites in his or her system.  For now, the laws remain active and prosecutors are using them.