LOOKING BACKWARDS: HOW THE STATE PROVES YOUR BLOOD ALCOHOL WAS HIGHER THAN YOUR BREATHALYZER RESULT

You had several drinks at the bar before you drove home. Police stopped you for a moving violation and arrested you for DUI.

At the police station, you agree to take the breathalyzer. The reading is .077, just below the legal limit. You think you are home free. But the prosecutor is now claiming your blood alcohol level was actually above .08 when you were driving.

Can they do that? What can you do?

Your body absorbs alcohol on a curve. After drinking, your blood alcohol rises and then starts to fall. These are called the absorption and elimination phases. The prosecutor uses a technique called retrograde extrapolation to calculate where you were on the curve at the time you were driving.

If you were in the elimination phase when you took the breathalyzer, the state can argue that your blood alcohol was actually higher at the time you were driving. The state uses an expert to determine where you were on the curve based on factors such as when and what you drank and whether you ate.

Are you now doomed? Not necessarily. An experienced DUI attorney can review the credentials of the expert, the factors used and look for holes in the expert’s opinion. Maybe the expert is speculating about how much you drank or when. Or the expert is assuming you were in the elimination phase without a real basis for that opinion.

Remember, the state must prove you guilty of all elements of DUI beyond a reasonable doubt. Without a solid expert opinion, the state may be unable to meet its burden of proof.

If you are charged with DUI or a related offense in Illinois, contact an experienced DUI attorney immediately. Even if the expert’s opinion is rock solid, an attorney who is respected in the court house may help you gain a better plea agreement than you could on your own.

If you have questions about this or another related criminal or traffic matter, please contact Matt Keenan at 847-568-0160 or email matt@mattkeenanlaw.com.

(Besides Skokie, Matt Keenan also serves the communities of Arlington Heights, Chicago, Deerfield, Des Plaines, Evanston, Glenview, Morton Grove, Mount Prospect, Niles, Northbrook, Park Ridge, Rolling Meadows, Wilmette and Winnetka.)