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Is Serum Blood Testing a Reliable Method for Drunk Driving Cases?

If you were arrested in Michigan for drunk driving, and your blood was drawn by the police, then your blood was almost certainly tested at the state lab in Lansing.  As it relates to testing for DUI alcohol level only, this forensic lab almost exclusively uses a scientific method called gas chromatograpy to attempt to determine a true blood alcohol level.  A “whole blood” sample is used for this testing method.  If you case involves drugs, then a mass spectrograph was added to the gas chromatograph.

In some cases, such as where the blood is testing at the hospital after your Michigan DUI arrest, or where the sample received at the state lab is corrupted, the blood will be tested using a far less reliable, accurate or precise method called “serum testing.”  For this reason, and others, it may be argued that serum blood results in a Michigan DUI case should not be used as evidence of guilt.

In a recent Illinois case[i] involving some of the issues with serum testing, the defendant was at a restaurant celebrating her friend’s birthday. Shortly after midnight, the defendant left the party and drove away in her vehicle. Ten minutes after she left she called her friend who was still at the restaurant and explained that she had driven off the road about 2.5 miles from the restaurant. Upon arrival, the friend observed that the defendant was sitting in her car crying.  She had ran off the roadway and believed she had a broken leg.

The defendant refused to go to the hospital and was walking down the side of the road. A 911 call was placed, and three police officers and an ambulance arrived at the scene.  One of the responding officers testified that when she arrived, defendant was on a stretcher in the ambulance. The officer detected a hint of alcohol emanating from defendant and observed that defendant’s eyes were red and bloodshot. Defendant explained that her vehicle had gone off the road, but she was not sure why. The officer concluded that defendant had driven off the road and interpreted the accident to indicate defendant was under the influence of alcohol.  At the hospital the officer placed defendant under arrest for DUI and requested that she submit to chemical testing for alcohol. Defendant refused the officer’s request for chemical testing. Defendant was later charged with DUI.

The friend from the restaurant testified that he was a former police sergeant, Breathalyzer operator, and accident reconstruction specialist. In his opinion, the defendant was not under the influence of alcohol. He believed that defendant had blown a tire, causing her to lose control and drive off the road.

A registered nurse treated the defendant at the hospital. She testified that defendant smelled of alcohol and admitted to consuming alcohol. She testified that, in the regular course of providing medical treatment, she drew defendant’s blood and subjected it to a blood alcohol test. The State offered into evidence the blood alcohol test report created by the hospital. Defendant objected to the report, arguing that it did not meet the requirements of a business record, in part because the report stated: “Results are intended to be used for medical purposes only and not for legal or employment purposes.”

The court overruled the defense’s objection and admitted the report as a business record. The court explained that defendant’s concerns about the veracity of the document were relevant to the weight the jury would give the document, but did not affect its admissibility. The hospital test record indicated defendant’s serum blood alcohol level was 190 milligrams per deciliter.

Outside the presence of the jury, the State requested that the court take judicial notice of the fact that 1.18 is the proper conversion factor to convert a serum blood alcohol level to whole blood alcohol level. In support of its request, the State cited to a provision of the Illinois Administrative Code (Administrative Code), which states, “The blood serum or blood plasma alcohol concentration result will be divided by 1.18 to obtain a whole blood equivalent.”

The court adapted the state’s proposed instruction regarding this matter which was given to the jury. The instruction read:

“In the course of this case, you have heard testimony about the results of a blood draw. There are two ways to measure blood alcohol concentration: by serum levels or by what is called whole blood. Whole blood is [the] standard used by law enforcement and legal proceedings, and it can be calculated by converting the serum level to the whole blood equivalent. In this case, the testimony was that the serum level was .190. The blood serum or blood plasma alcohol concentration results will be divided by 1.18 to obtain a whole blood equivalent. After conversion, the whole blood equivalent is .161.”

On appeal the defendant claimed the instruction was improper because the jury was not instructed that “it did not have to apply the conversion factor.”

The appeal’s court concluded that the trial judge erred by submitting this jury instruction because it does not comply with the rules of evidence concerning judicial notice.  Specifically, the appeals court found it significant that the instruction was not limited to the single judicially noticed adjudicative fact, that is, the applicable conversion factor set out in the Administrative Code. Instead, the instruction contained another reference to a second significant piece of evidence, defendant’s purported blood serum level, which was not subject to judicial notice and had been introduced to the jury during the testimony of nurse.

Consequently, the court found that the instruction became “somewhat testimonial” in that the court provided the calculations for the jury using a formula that included a contested fact, the defendant’s actual blood serum level, multiplied by the conversion factor of 1.18, and the case was remanded back to the trial court.

There are many problems with this case, such as the fact that it ignores the wide range of potential conversion rates that might be applicable to serum blood testing.  One good thing about this case is that it does address the fact that it is up to the jury, not the judge, to decide what the appropriate conversion rate should be in any particular case.


[i] People v. Love, 2013 IL App (3d) 120113, 996 N.E.2d 735 (Ill.App. 3 Dist., 2013)

About Patrick Barone

Patrick Barone
Patrick T. Barone is the Founding Partner and CEO of The Barone Defense Firm with offices throughout Michigan. Mr. Barone is the author of two books on DUI defense including Michigan DUI Law: A Citizen's Guide and the well respected two volume treatise Defending Drinking Drivers (James Publishing),a chapter in Defending DUI Vehicular Homicide Cases, 2012 ed. (Aspatore Books), an adjunct professor at the Thomas M. Cooley Law School, and a graduate of the Gerry Spence Trial Lawyer’s College. Mr. Barone has an “AV” rating from Martindale-Hubbell and since 2009 has been included in America’s Best Lawyers.

If you would like to contact the author, please visit: http://www.yourmichiganduilawyer.com


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