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You are here: Home / Criminal Defense / Why Your DWI Urine Test is Not Accurate

Why Your DWI Urine Test is Not Accurate

Barry S. Edwards · Jul 1, 2011 · Leave a Comment

Minnesota law enforcement insists on testing drivers’ alcohol content using an unreliable testing method.  At the Barry S. Edwards Law Office I know the flaws in the prosecutors’ case and can challenge the use of DWI urine tests.

The expert scholarship on the science of Minnesota’s drug testing procedures is unrefuted. Common sense, good science, and good law have taken a back seat to the inertia of the status quo.

1. Collection

Under the Minnesota Administrative Rules, a blood test may be administered by a “person who has been trained as a physician, registered nurse, medical technologist, medical technician, physician’s trained mobile intensive care paramedic, or laboratory assistant” while administration of a breath test requires a “person who has satisfactorily completed a course . . . in the use of an instrument specially manufactured to analyze a specimen of breath.” When it comes to urine collection, however, the Rule states only that “[a]ny person may administer a urine test.” Minn. R. 7502.0300, .0400, and, 0500.

Without belaboring the science or getting bogged down in hypotheticals, there are many ways in which a sample collected by “[a]ny person,” rather than someone trained in chain-of-custody, sample preservation, and contamination, can be mislabeled, subjected to unwanted chemical processes, or contaminated.

At a minimum, a proper urine collection kit must have an agent to prevent sugars from fermenting (if the sugars are allowed to ferment, the result will be a higher ethyl-alcohol concentration than the original sample due to the by-products of fermentation.). Proper refrigeration is also necessary to prevent corruption of the sample. See, e.g. California’s “Urine Collection for Blood Alcohol Instructions” (providing for specific training and collection procedures for urine alcohol content) and Wisconsin’s “Ethanol and Common Volatiles by Headspace Gas Chromatography” (same) (on file with the author). While a test can account for subsequent fermentation, Minnesota does not perform this simple test, as discussed below.

2. Testing

The greatest concern regarding urine collection is Minnesota’s “first-void” protocol. Minnesota tests a first-void urine sample, urine collected from a driver upon arrest without having the driver void his or her bladder before providing a sample for testing. As a result, the urine tested is the urine pooled in the driver’s urinary bladder since the driver last voided (urinated) which does not accurately reflect the alcohol concentration in the driver’s blood at the time the alleged offense occurred. So, if a driver drinks to a 0.08 blood alcohol concentration, then waits two, six, or eight hours before driving , but does not urinate before doing so, the urine tested will contain the alcohol that has since been metabolized and no longer indicates the driver’s level of intoxication.

The scientific literature clearly states that first-void urine testing is not an accurate measure of intoxication: “An unusually long residence time in the bladder will tend to skew the UAC/BAC [urine alcohol concentration / blood alcohol concentration] ratio because UAC reflects the BAC at the time when urine is formed and not the BAC at the time of voiding.” “Urine as a Biological Specimen for Forensic Analysis of Alcohol and the Variability in the Urine-to-Blood Relationship” Alan W. Jones, Toxicology Rev. 2006; 25(1):15-35. The author has twenty-four peer-reviewed scientific articles as well as expert affidavits and transcripts of expert trial testimony on file in support of the scientific conclusion that the urine tested via Minnesota’s first-void protocol does not reflect the driver’s level of impairment.

The State of Minnesota is aware of this problem. A Minnesota BCA memo on file with the authors shows BAC and UAC tests of specimens collected from the same individual at the same time. Collected on January 22, 2006 at 04:30, the urine sample revealed 0.12 grams of alcohol per 67 milliliters of urine while blood collected at the same time revealed 0.09 grams of alcohol per 100 milliliters of blood (the corresponding statutory units of measurement per Minn. Stat. §169A.03, subd. 2). The discrepancy is obvious and marked. Pooled urine does not accurately reflect a driver’s level of intoxication at the time of the alleged offense.

The Minnesota BCA could control for such variations by using well-tested ethyl glucuronide (EtG) and ethyl sulphate (EtS) tests or glucose tests which detect residual alcohol that has been metabolized (and can be subtracted out) and alcohol fermentation in a sample that has been stored outside a live body’s urinary bladder, respectively. The BCA does neither.

Tuesday (July 5): the Constitutional implications of Minnesota’s urine test protocols.

(Thanks to Charles Ramsay, Ramsay Law Firm, PLLC for sharing his research)

Criminal Defense DUI, DWI, Urinalysis

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About Barry S. Edwards

Barry S. Edwards is a criminal defense attorney. He provides personalized attentive legal solutions and representation for individuals in Minneapolis, St. Paul, and surrounding Minnesota communities. Read More…

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