Forensic Methods Used to Analyze Restricted Substances in Blood for an OWI Case

An OWI conviction is dreaded because it leads to consequences that include social stigma and possible jail time. Such convictions sometimes include news articles and public records our colleagues and neighbors may see on their computer and television screens, newspapers, or even tabloid magazines. However, what happens in a Wisconsin forensic science lab before evidence convicting an individual of an OWI (illegally driving under the influence of drugs or alcohol) can be presented in court? 

Legal blood or breath concentration for alcohol in Wisconsin

In the event your alcohol concentration in either your blood or breath is .08 or higher while driving in Wisconsin, you will face BAC/PAC charge for driving with a prohibited alcohol concentration. For drivers with three or more previous OWI convictions, the legal limit is .02. Breath testing is usually performed locally at a jail, sheriff’s department, or police station. Blood is usually drawn at a local hospital but sometimes can be drawn at a jail by a qualified person. Blood samples are then sent to be tested at a State certified laboratory and the report will state an individual’s BAC in units of grams per 100 milliliters of whole blood.

Legal concentration for drugs in Wisconsin

It is illegal in Wisconsin to operate a vehicle with “any detectable amount of a restricted controlled substance” in the blood. Restricted controlled substances include delta-9 THC, cocaine, methamphetamines, and other highly controlled substances. Drugs that are prescription or even over-the-counter medications can be considered as adding to alcohol or as themselves causing impairment and can be the basis for an operating while impaired case.

What is the primary instrument used in a forensics lab to test the amount of alcohol or drugs in a blood specimen (sample)?

The Wisconsin State Laboratory of Hygiene tests for the amount of alcohol in blood specimens by using gas chromatography. What is a chromatograph, you may ask? A chromatograph is a scientific instrument used to separate the chemical substances present in a blood sample. The aim of this is to separate out the ethanol in a blood sample and determine how much ethanol is in the sample.

Initially the laboratory procedures in Wisconsin primarily work to detect and quantify ethanol, but might also look for other volatile substances (such as DFE which is 1,1 diflouroethane and comes from inhalants). If the alcohol concentration is low or if other drugs are suspected, further analysis is done. The laboratory will screen to determine if other commonly used drugs may be present in the blood sample. If screening shows there may be other drugs present, further analysis is done. In addition to looking for particular drugs, the metabolites of those substances are usually analyzed as well. Metabolites are the form a drug takes in the body after it is chemically changed from its original form. Metabolites can indicate how much of and when a drug was taken based on how long it takes to break down within the human body.

A Science-Based Approach to Defending OWI Case

At Welch & Schmeiser Criminal Defense Group we are specially trained in the science of OWI evidence collection and analysis and are familiar with possible ways to challenge the accuracy of blood and breath tests. Sarah Schmeiser has earned the Forensic-Lawyer Scientist designation from the American Chemical Society. Our knowledge and guidance could mean the difference between facing a conviction and having your charges dismissed. You can contact our Madison offices at 608-839-7750 or schedule a free consultation by email. We handle OWI cases throughout central and southern Wisconsin.