Here's the scenario: You’ve had a few drinks, waited a bit, and now you feel okay to drive. You're alert, steady, and confident. Then you see blue lights in your rearview mirror—and your blood alcohol concentration (BAC) still reads over the legal limit. What gives?
This isn’t just a matter of bad luck or faulty equipment. What you may have experienced is a well-documented scientific phenomenon called the Mellanby Effect. It is important to understand this concept so that you can make informed decisions about when it's safe to drive, and what your BAC might be if you decide to give a breath sample.
What Is the Mellanby Effect?
Named after British physician Edward Mellanby, who first studied the effect in 1919, the Mellanby Effect refers to the difference in how impaired someone feels as their BAC is rising versus when it's falling—even if the BAC level is exactly the same at both points in time.
In plain English? You often feel more drunk while your BAC is rising than you do at the same BAC level on the way down. This is why someone may feel “sober” or “fine to drive” even though they’re still over the legal limit.
Here’s an example:
Let’s say your BAC is 0.08%—the legal limit in Mississippi. On your way up to that BAC, you may feel tipsy, relaxed, or uncoordinated. But later, as your BAC declines to 0.08%, you might feel sharper and more in control. Unfortunately, your body doesn’t functionally sober up just because you feel better.
Why It Matters in a Mississippi DUI Case
In Mississippi, DUI charges can be based on:
Your BAC being at or above 0.08% (known as a “per se” violation), or
Observable signs of impairment, regardless of your exact BAC.
This means that even if you don’t feel impaired, you can still be charged—and convicted—based on breath test results or observed behavior during a traffic stop.
Officers are trained to recognize signs of impairment, and these signs may still be present even as your BAC is decreasing. You might not slur your words or stumble, but subtle signs—like slowed reaction time or poor performance on field sobriety tests—can still show up. The Mellanby Effect explains why this happens.
The Science Behind It
According to the 2023 NHTSA SFST Participant Manual, “a person feels more impaired while his/her BAC is still rising, than at the same level while his/her BAC is declining. The person is not less impaired, but they ‘feel better’” (Session 2, pg. 43). This false sense of sobriety can lead to dangerous decisions—like getting behind the wheel when you're still legally drunk.
Takeaway for Drivers in Mississippi
The Mellanby Effect is real—and it’s something both law enforcement and prosecutors understand well. Whether you feel sober or not, if your BAC is over the limit, you're at risk of a DUI charge.
If you or someone you care about has been arrested for DUI in Mississippi, it’s important to understand that perception doesn’t equal protection. Scientific concepts like the Mellanby Effect can become critical in building your defense—or in challenging the evidence presented against you.
Talk to a Mississippi Criminal Defense Lawyer Who Knows the Science Behind DUI
At the Eichelberger Law Firm, we understand how human physiology, law enforcement training, and field sobriety tests all come together in DUI cases. Lead attorney Matt Eichelberger has the experience to spot weaknesses in the state’s case—and to fight for your rights every step of the way.
Call us today for a free consultation. Don’t wait until your “gut feeling” of sobriety becomes a legal nightmare.