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  • Writer's pictureDavid A. Cmelik Law PLC

Iowa DUI lawyer explains breath test

The Datamaster DMT is the machine certified to obtain evidentiary DUI breath tests in Iowa. It is usually the second breath test administered and is always conducted inside a law enforcement center or jail. Think of the “D” in Datamaster DMT as “desktop.” Think of the “P” in PBT, or, roadside test, as “portable” and “preliminary.” In this article, we’ll be discussing the desktop test—which can be used as evidence of intoxication before the jury in an Iowa criminal prosecution for Operating While Intoxicated, or, OWI, our version of DUI.


The desktop breath test machines used in each county are maintained by the Iowa Department of Public Safety and recertified each year for continued use. There is usually at least one in every county. In Linn County, which includes Cedar Rapids and surrounding area, is assigned two such evidentiary desktop breath test machines—one at the Linn County Correctional Center Sobriety Testing and OWI Processing Center (called “STOP” for short) and the Marion Police Department in Marion, Iowa.


The evidentiary Datamaster DMT, or, desktop breath test, is a self-diagnosing, internet-connected device. When it experiences a “fault code,” much like the check-engine light in your car, it will “throw” an error code. These codes are specific to errors and disrepair.


Some errors include a “negative slope” and “invalid sample.” When the machine registers ever increasing volume of air but ethanol registers a spike and then rapid real time decrease, the machine is programmed to throw an error code for “negative slope.” A negative slope indicates anomalous, or, unusual and unexpected spikes and drops in ethanol that would not occur in deep lung air. Such a spike and drop might indicate residual mouth alcohol unrelated to ethanol in the lungs—in chewing gum or regurgitated stomach acid. Because this is usually the case, Iowa Department of Safety Protocols require that the officer wait 15 minutes—called deprivation time—ensuring no food or drink enters the subject’s mouth and restart the test.


In a different kind of error code, when police or sheriff departments in Iowa store cleaning solvents or place hand sanitizers too close to the DUI breath test machine, the desktop DUI breath test machine may sense ethanol without the initiation of a test. This is an ambient ethanol failure. Departments are urged to store cleaning solvents and hand sanitizers away from the Datamaster DMT breath test station.


Another code occurs when officers place radios and cell phones too close to the DUI breath test machine. The machine will sense and throw a code for radio frequency, or, RF interference.


A good DUI criminal defense attorney in Iowa will explore your best options for a favorable outcome by examining both the maintenance record of the machine used for a drunk driving breath test and the specific receipt it prints in a memory test for evidentiary purposes. Such examination may, but not always, reveal defects in the investigation and scientific testing.

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