How accurate are blood alcohol tests and can they be challenged or beaten in court?

There are two primary methods used to measure a suspected drunk driver’s bodily alcohol content for criminal prosecutions: breath and blood tests.

Breath tests are more frequent because of the ease of administration and quick results. Blood tests are conducted typically when a breath test is refused or when a breath test is not practical due to accident, injury or medical issue. Those arrested for suspicion of DUI that have submitted to a blood test may wonder if they are worse off than those having submitted to a breath test. This is not necessarily true. There are more sources of error in a blood test and typically include the following:

Delay in Sample Collection

A blood alcohol test requires a blood sample be collected off site and after the attempted administration of a breath test. This usually means that the collection does not occur for up to two hours, or more, after driving. Because there is a delay in the blood collection the result is usually not an accurate reflection of the alcohol content at the time of driving which is what is most important. A suspect’s BAC is never the same at two different times. It is either rising or falling depending upon the amount of alcohol consumed, the time of the last drink and rate of absorption and elimination. This is also affected by body weight and gastric contents. Because law enforcement rarely has the information necessary to make that determination, a person’s BAC may be difficult to determine by the prosecution but easier for the defense.

Ensuring Sample Collection was Reliable

Michigan law requires that only a physician or a qualified individual operating under the direction and supervision of that physician perform the blood draw and using a specific blood collection kit with specific instructions. The law also requires that the blood draw be performed in the proper medical environment. There are many requirements here that if not followed could be used to argue the blood result is not reliable and/or otherwise inadmissible. If the sample was collected by a paramedic at the jail a good challenge can be made. Typically fire department paramedics are not supervised by a doctor.

Delivery of the Sample Must be Timely

The blood sample must be delivered, either by hand or us mail, immediately after collection. There exist preservatives within the collection tube to ensure against spoliation, clotting and alcohol fermentation. The date the sample was received by the lab is reported on the results. It must be inspected in every case. It is not infrequent that the blood was stored somewhere before mailing. Sometimes in the back or trunk of a police car. If there is a delay in delivery, legitimate questions exist like why, where was it and was it refrigerated or subjected to high temperatures. Anything other than prompt delivery will place the reliability and accuracy of the sample in question.

Analysis of the Blood Sample is Performed on a Large Scale

The Michigan State Police Forensic Science Division is responsible for performing the analysis of the blood for identification, quantification and reporting. The MSP-FSD is overworked and understaffed. They utilize a method called headspace gas chromatography using a flame ionization detector system. This method is reliable but only when the sample is prepared properly and the ethanol standards used for comparison are properly measured and stored. The lab typically analyzes approximately 65 unknown samples at a time which is a large number. It generally takes several hours to prepare each of these samples for analysis along with the standards and controls necessary for each run. As one can imagine, the higher the number of sample preparation necessary for analysis, the higher the rate of error. Further, if the instrumentation is not working at optimal levels, the analysis can be susceptible to “carry over” meaning that alcohol from one sample can carry over to another. When carry over has been identified, the entire run must be repeated. The problem is re-doing an entre run is time intensive. For a department that is already overworked, it is less likely to happen. In order to evaluate the reliability of a blood analysis, the data from the entire run needs to be reviewed.

Reporting of Sample can be Misleading

On its face, the FSD reports what it calculates as its uncertainty of measurement, which can be approximately 10%. It changes every year and that number is subject to scrutiny as the FSD are the ones who calculate it. If an outside organization were to calculate it, the number would likely be higher due to bias. Remember, the Forensic Science Division is a part of a law enforcement agency.

Fighting a Blood Alcohol Test

Blood alcohol testing can be a reliable and accurate manner of bodily alcohol content only when each of the several stages has been verified for proper performance. Because there are so many different sources for potential error a blood test can have a higher rate for error than a breath test. In other words, there are many different angles to demonstrate a reasonable doubt in a blood test’s accuracy and reliability.

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Attorney Morris has enjoyed a very successful and distinguished career as a trial lawyer providing high quality legal representation in the area of state and federal criminal defense for 19 years. He is known for his trial preparation by fellow attorneys, judges and clients alike. As a trial attorney, he is dedicated to attaining justice in every case, and is prepared to take on complex legal issues with success. Barton and his law firm pride themselves on obtaining results for their clients that other attorneys cannot. Not only does Barton Morris have extensive experience, he also engages in continuing legal education to provide the highest quality legal services. Barton has received specialized scientific training through the American Chemical Society. He attended the prestigious Trial Lawyers College and serves on its Alumni Association Board of Directors. Barton Morris is also a board member of several distinguished legal associations including the Michigan Association of OWI Attorneys, and the DUI Defense Lawyer’s Association Justice Foundation. He is also an active member of the National Association of Criminal Defense Attorneys and has also graduated from their National Criminal Defense Trial College in Macon, Georgia. Barton Morris was chosen as a Top Lawyer of Metro Detroit for 2012, 2013 & 2014 for DUI/DWI and criminal defense by DBusiness Magazine and Hour Magazine. Barton Morris was also chosen as a Super Lawyer in Criminal Defense for 2014-2017 and Barton Morris is the only Lawyer in Michigan designated by the American Chemical Society as a “Forensic Lawyer-Scientist”
December 27th, 2016|