Blood Drug Levels Never Predict Drug Effect Or Impairment!

As a seasoned Georgia Drug DUI Attorney with over 30 years of experience defending clients against DUI charges, I’ve seen firsthand how prosecutors and state experts often rely on blood drug test results to paint a picture of impairment. But here’s the truth that shatters their case: Blood drug levels alone can NEVER accurately predict drug effects or impairment in an individual. This isn’t just my opinion—it’s grounded in over a century of medical pharmacology research, as highlighted by experts like Dr. Stefan Rose, a renowned forensic toxicologist and psychiatrist.

In Georgia, where DUI laws focus on whether a driver is “less safe” due to impairment (O.C.G.A. § 40-6-391), blood tests are frequently used as evidence in drug-related cases. However, these tests are fundamentally flawed when it comes to proving actual impairment. Let’s dive into why, drawing from established pharmacology principles that every defense attorney—and judge—should know.

The Myth of “Therapeutic” or “Toxic” Blood Drug Levels

Prosecutors love to trot out tables of so-called “therapeutic” or “toxic” blood drug levels, claiming they indicate impairment. But these tables are based on outdated, flawed data and don’t hold up under scientific scrutiny. As Dr. Rose explains, there’s simply no such thing as a single blood drug level that predicts any pharmacologic effect in a person. This false narrative is often pushed by state chemists to bolster prosecutions, but it’s not supported by evidence.

In fact, published ranges are only marginally useful in one scenario: when the measured level is lower than any listed in those tables. In that case, it might rule out certain effects. Otherwise, relying on a single test result ignores the complexities of how drugs interact with the human body.

Why a Single Blood Test Can’t Tell the Whole Story

To understand this, let’s break down three key pharmacology concepts from medical textbooks like Goodman and Gilman’s The Pharmacological Basis of Therapeutics—the gold standard used worldwide.

1. 1. Single Oral Drug Dose and the Blood Drug Curve
      When someone takes a drug orally (e.g., a pill or edible), the concentration in their blood rises to a peak and then declines over time. A single blood test is like taking a snapshot at one random point on this curve. Without knowing when the drug was ingested, how much was taken, or the individual’s metabolism, it’s impossible to determine where on the curve the person was at the time of driving. Were they on the way up (potentially feeling effects increasing) or on the way down (effects waning)? The test can’t say, making it useless for predicting impairment.

1. 2. Multiple Oral Doses and Steady-State Fluctuations
      For people taking drugs repeatedly (e.g., prescription medications), blood levels fluctuate even more. After multiple doses, the body reaches a “steady state” where levels oscillate between peaks and troughs. Again, a single blood draw captures just one moment— it could be at a high point right after a dose or a low point hours later. Predicting past effects or impairment from this? Scientifically impossible. This is especially relevant in cases involving chronic users or those on maintenance therapy, where tolerance further complicates the picture.

1. 3. The Blood Drug Level-Response Curve: The Nail in the Coffin
      Perhaps the most damning evidence is the blood drug level-response curve, which plots drug concentration against physiological response. In studies, individual responses vary wildly—even at the same blood level, one person might show no effects while another experiences significant ones. Factors like genetics, age, health, tolerance, and interactions with other substances make each person’s curve unique. A single test result can’t place someone on this curve or predict their response. As Dr. Rose puts it, this one graph alone explains why blood tests can NEVER reliably indicate impairment in an individual.

These principles aren’t fringe theories; they’re foundational to medical pharmacology and have been validated through decades of peer-reviewed research.

Real-World Implications In Georgia DUI Cases

There is no “cheat sheet” comparing lab report levels to expected impairment despite government lab technicians claims to the contrary. We have heard reports of drivers facing vehicular homicide charges based on a delta-9 THC levels as low as 1.9 ng/mL—barely above the margin of error—only admitting to cannabis use two days prior and no field sobriety tests indicating impairment. The driver claimed fatigue from overnight driving caused the accident, not drugs. Cases like this highlight how overreliance on blood levels can lead to unjust charges.

In Georgia, where there’s no per se limit for most drugs (unlike alcohol’s 0.08% BAC), the state must prove actual impairment. Blood tests might show presence, but they don’t prove effect. We have seen cases where a daily smoker of marijuana’s blood tested as high as 9 ng/ml of active THC but the video showed no impairment. Daily smokers can have elevated THC but no effect due to tolerance.  As your attorney, I can challenge these results by cross-examining state experts on these pharmacology flaws, potentially getting charges reduced or dismissed.

Arm Yourself With Science—Contact George Creal Today

If you’re facing a drug DUI charge in Georgia, don’t let misleading blood test evidence seal your fate. With a deep understanding of forensic toxicology and pharmacology, I can dismantle the prosecution’s case and protect your rights. Whether it’s marijuana, prescription meds, or other substances, remember: Presence ≠ Impairment.

For more insights, check out resources from experts like Dr. Stefan Rose at University Medical and Forensic Consultants (www.umfc.com), who offers consultations and educational materials on this topic.

Ready to fight back? Call George C. Creal, Jr., P.C. at (770) 961-5511 or visit www.georgialawyer.com for a free consultation. Let’s turn science into your strongest defense!