Traffic Safety Testing


The Forensic Toxicology section provides alcohol and drug analysis for law enforcement agencies in support of Wisconsin Statue 343.305 (impaired driving). The section also tests specimens collected in the investigation of the impaired operation of boats, snowmobiles and all-terrain vehicles. The section tests approximately 20,000 specimens annually for police agencies, sheriffs’ offices, the Wisconsin State Patrol and the Wisconsin Department of Natural Resources. When required, staff members provide testimony in court on laboratory findings, methods of analysis and interpretation of results. Section members receive more than 4,000 subpoenas and make more 300 court appearances annually.


Blood Specimens

Blood specimens collected for investigation of operating while impaired (OWI) offenses are fluoride preserved whole blood. Use the tubes provided in the WSLH collection kit. It is normally desirable to collect two tubes of blood; however, an alcohol analysis alone may be completed with as little as 0.5 mL (approximately one-half inch of blood in the tube). Minimal drug testing requires approximately one half of a tube (~4 mL). Other types of blood specimens (unpreserved whole blood, serum, plasma) can be tested but are not recommended.(View collection directions.)


Urine Specimens

Urine specimens collected for investigation of operating while impaired offenses are collected without preservative. Use the materials provided in the WSLH collection kit. Pay particular attention to the collecting procedure: Discard the “void” specimen and collect the second specimen produced. A URINE SPECIMEN IS NOT ACCEPTABLE FOR DRUG TESTING FOR IMPAIRED OPERATION. (View collection directions.)


Order Collection Kits

To order sample collection kits, use the Forensic Toxicology Impaired Driving/OWI Kit Order Form.


How is the Testing Done?


Alcohol Testing

Specimens submitted for alcohol analysis are tested by gas chromatography. The method is specific for ethanol (ethyl alcohol). The reported value for ethanol concentration is accurate within 5% of the value, or +/- 0.005 g/100 mL, whichever is greater.


Drug Testing

Specimens submitted for drug testing are analyzed following forensic protocols. Specimens are initially screened by High Resolution Mass Spectrometry. Those specimens that have positive initial screens are re-analyzed using alternate methods. Additional quantitative procedures may be required. The testing procedures detect prescription drugs, over-the-counter drugs, illicit drugs, and some drug metabolites. While these procedures will detect a broad range of drugs, some drugs cannot be detected with current WSLH methodology or are detected only by special procedures. A history of suspected drug exposure is helpful to ensure that all drugs of interest are monitored.


Drug Testing Policies

Due to limited resources the WSLH may limit the amount of testing performed on requests for comprehensive blood drug testing when the alcohol concentration is in excess of 0.100 g/100 mL or a restricted controlled substance has been confirmed. The testing that is offered is sufficient to support per se alcohol/drug charges.

  • If the blood ethanol concentration exceeds 0.100 g/100 mL, all drug testing requests will be canceled.
  • If a full drug panel is requested and delta-9-tetrahydrocannabinol (Δ-9-THC), cocaine and/or cocaine metabolites or other Restricted Controlled Substances (346.63(1)(am)) are detected, no drug testing will be conducted beyond the restricted controlled substances.

If the case involves a Drug Recognition Expert (DRE) evaluation, sufficient testing will be conducted to support the DRE opinion.

Drug testing will be performed on fatal or great bodily harm crash cases, regardless blood alcohol concentration.


How are the results reported?


The results of the testing are reported by mail. Copies of the WSLH reports are mailed to the subject and to the submitting agency. The Wisconsin Department of Transportation receives an electronic copy of the blood ethanol concentration of arrested drivers.


Interpreting The Report


Alcohol Results

The ethanol concentration is reported in concentration units, grams per 100 milliliters of whole blood. Urine ethanol concentrations are converted to corresponding blood alcohol concentrations, as per Wisconsin Statute 885.235(2). The state of Wisconsin has numerous prohibited blood alcohol concentrations, depending upon the particular circumstances of the subject. The Wisconsin Statutes or an attorney can help identify which circumstances apply.


Other Drug Impairment

Drivers in Wisconsin are prohibited from operating while they are impaired by drugs, regardless if the drugs are illicit, over-the-counter, or taken as prescribed by a doctor. Consequently, specimens testing positive for drugs other than alcohol require individualized interpretation.

Any drugs detected are reported either as “Present” (indicating that the drug was detected and confirmed but not quantitated) or as a quantitative concentration of drug, expressed as micrograms per milliliter (mcg/mL) or nanograms per milliliter (ng/mL).


Zero Tolerance for Illicit Drugs

It is illegal to operate a motor vehicle with any detectable amount of a restricted controlled substance in the driver’s blood. Restricted controlled substances include all Schedule I controlled substances, with delta-9-tetrahydrocannabinol (Δ-9-THC) as the specific tetrahydrocannabinol, plus methamphetamine, cocaine and cocaine metabolites from Schedule II. This law does not apply when there is a valid prescription for the legitimate medical use of methamphetamine, a drug that metabolizes to methamphetamine, GHB or marinol (medical Δ-9-THC).


Post-testing Concerns


Unexpected Results

These may arise when the presence or absence of alcohol and/or drugs is reported when another result was anticipated. These may also include reports of unexpectedly or extraordinarily high concentrations of an analyte. As there can be a number of possible reasons for the laboratory obtaining results which you did not expect, please call the laboratory at 608-224-6241 to discuss your concerns.


Specimen Availability

Specimens are discarded after six months. Specimens submitted to the Forensic Toxicology section are routinely retained for six months following the date of the final report. Specimens will be saved beyond this time upon written request from the submitter or subject. The specimens will be saved an additional two years from the date of the request. The WSLH cannot honor requests to save samples for indefinite periods of time.


Specimen Re-analysis

The specimen may be re-analyzed for ethanol concentration upon written request of the subject, the submitting agency or the prosecuting authority. The re-analysis may be conducted by the WSLH Toxicology section or the specimen may be sent to another laboratory. The WSLH Toxicology section will perform the re-analysis for a pre-paid fee of $53 and will issue a report of the results to all parties connected with the specimen.

Certain requirements must be met if the specimen is to be tested by another laboratory. The submitting agency or prosecuting authority must give written permission to release the specimen to the selected laboratory, and arrangements must be made with that laboratory to accept the specimen and to pay for the cost of the testing. WSLH will assume no role or responsibility other than to package the specimen, enclose the request letter (or other documents provided by the requesting party) and mail the specimen. The WSLH does not currently charge for processing retest sendouts.

Please call the laboratory at 608-224-6241 for more information about specimen retesting.


Court Issues and Analyst Testimony

The Forensic Toxicology section is an analytical laboratory and not a branch of law enforcement. While the laboratory results will influence the progress of a case through the judicial system, the laboratory staff does not make legal decisions. The disposition of a case is controlled by the prosecuting authority.

The analytical staff is always willing to discuss the methods used in testing specimens and to assist in interpreting the results. Staff members are not trained in law, however, and do not give legal advice.

The Forensic Toxicology section serves all of Wisconsin, and as a section receives multiple subpoenas per working day. This volume of subpoenas often makes scheduling a particular analyst for a court appearance challenging. Please do not send subpoenas until after analyst availability has been determined by calling Court Scheduling at 608-224-6242. Subpoenas should be mailed to the analyst. Videoconference or telephone testimony is encouraged whenever possible.


Where to get more information


Call the Forensic Toxicology section at 608-224-6241. Mailed correspondence should be addressed to:

Forensic Toxicology
Wisconsin State Laboratory of Hygiene
2601 Agriculture Drive
PO Box 7996
Madison, WI 53707-7996


General FAQ


WSLH Forensic Toxicology Outreach