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Ohio DUI Defense: BAC DataMaster and “Interference”

Dayton DUI Attorney Charles Rowland > DUI Law  > DUI Process  > Ohio DUI Defense: BAC DataMaster and “Interference”

Ohio DUI Defense: BAC DataMaster and “Interference”

What Does It Mean When My BAC DataMaster Ticket Shows an Interfering Substance?

HOW IT WORKS: The BAC DataMaster is made with two filters which work to assure that only ethanol is present in a test result.  The filters rely on simple chemistry (different absorption curves/different micron levels for interferants) to prevent acetone, methanol, isopropyl or other interfering substances from artificially increasing the result.  When an interferant is present the two filters try to reach the same ethanol result.  To get to the same ethanol level, the machine subtracts the interfering substance (derived from one of the filters) from the total ethanol reading.  There is no way to know what the interfering substance is, only that it is present.  Theoretically, two interfering substances (both specific to each filter) could, in fact, interfere to such an extent that the test is too high and the machine does not have a mechanism for such an event.

According to the DataMaster Basic Operator Guide (hereinafter “Guide”), “If the DataMaster detects a chemical substance other than ethanol (acetone, methanol, isopropyl, etc.) the instrument will display and printout “INTERFERENCE.”  Depending on your software, the test may or may not be aborted and a print of the results may or may not be done.” Guide at p. 6.

OHIO AND JUNK SCIENCE: Not surprisingly, Ohio does not follow the majority of states in aborting the test, but allows the test to go forward with the actual level of interference printed on the BAC DataMaster ticket. (The ticket is the pink paper upon which the “result” of the breath test is printed.) An argument can be made that the decision whether or not to abort the test is reserved exclusively to the state and cannot be challenged.  This argument is unique to Ohio because of the decision in State v. Vega, 12 Ohio St.3d 185, 465 N.E.2d 1303 (1984). The Ohio DUI/OVI Blog has written extensively on why this is an absurd public policy position. (See State v. Vega, shackling Ohioans for over 25 years!, Junk Science in Ohio DUI/OVI Cases and Dayton DUI; Appearing on Fox45 Dayton’s New Source.

If you are charged with a DUI (now called OVI) wherein you took an evidential breath test, contact Charles M. Rowland II at 937-318-1DUI or 1-888-ROWLAND or visit www.DaytonDUI.com.  Just because you blew over the legal limit does not mean you are guilty!

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Charles Rowland


Charles M. Rowland II has been representing the accused drunk driver for over 20 years. Contact him at (937) 318-1384 if you find yourself facing a DUI (now called OVI) charge.

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