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Charles T. Ganz

Can a hospital blood sample be used to prove drugged driving?

On Behalf of | Feb 28, 2023 | Drug Crimes

Many people regularly take prescription drugs for a medical condition or occasionally use recreational drugs. If after the passage of time they do not feel high or otherwise intoxicated, they may feel it is safe to drive.

This sense of security can cause problems, however, if you are injured in a car crash and sent to the hospital. If the hospital performs a blood test, can it be used as evidence that you were driving under the influence of drugs?

Blood samples

If you are sent to the hospital following a crash, the hospital will likely not collect a blood sample unless medically necessary, not even to test for drugs.

If the hospital does collect blood to test for drugs, it generally only looks for specific drugs. These screening tests have a significant false-positive rate.

If police want the hospital to perform a blood test for a full toxicologic screening of drugs, the police must obtain a valid search warrant to do so.


Even if a hospital blood test uncovers drugs in your system, this does not automatically mean that you were impaired at the time of the crash.

Hospital blood tests measure the presence, not the quantity, of drugs in your system. Even if the quantity of drugs in your system was ascertained, in Texas, there is no per se level of drug impairment that proves a motorist was driving under the influence of drugs.

The time of ingestion is important but cannot always be identified. A drug taken hours or even days earlier can remain in your system long after any impairment has worn off.

Moreover, every person metabolizes drugs differently. The dosage one person takes can affect them differently from someone else who took the same dosage.

So, instead of relying on blood tests to detect impairment, often, specially trained officers will look for visual indicators that you are under the influence of drugs. Police may also look in plain sight for evidence of drugs or drug paraphernalia in your vehicle.

Even if police find supposed evidence of drugs or through observation believe that you are under the influence of drugs, this does not automatically lead to a conviction. Police bear the burden of proving beyond a reasonable doubt that you were impaired by drugs for there to be a conviction for drugged driving.