DR. CURT E. HARPER
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DUI (Drugs & Alcohol)

Examining how alcohol and drugs impair driving, and the science behind toxicology testing.
Driving under the influence, whether from alcohol (DUI) or drugs (DUID), is a leading cause of accidents, arrests, and legal disputes across the United States. Both alcohol and drugs—prescription, over-the-counter, or illegal—can impair a driver’s ability to operate a vehicle safely by affecting judgment, coordination, and reaction times.

In DUI cases, blood alcohol concentration (BAC) is typically measured through breath, blood, or urine tests. The legal threshold in most states is 0.08% BAC, though impairment can occur even at lower levels.

In DUID cases, testing may involve 
blood, urine, oral fluid, or hair samples
 to detect substances such as opioids, stimulants, sedatives, cannabis, or other impairing drugs.

Because each substance interacts with the body differently, and because absorption, metabolism, and elimination vary between individuals, toxicology results play a critical role in determining the extent of impairment at the time of arrest or accident. Legal outcomes often hinge on understanding not just the presence of alcohol or drugs, but how those substances actually impacted the driver’s performance and decision-making.
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DR CURT E. HARPER

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