How DUI Toxicology Testing Usually Works
When police suspect drugs, they usually seek a blood sample. The lab then runs DUI toxicology testing to look for drugs or their byproducts. Many labs use two stages, a screening test and a confirmation test.
A screen is broad. A confirmation test targets a specific substance and gives a more exact answer. The lab report should say which methods it used. When it does not, that gap is worth raising early, before anyone relies on the result.
The Legal Basis for Drug Testing
Under Vehicle Code section 23612, the law treats a driver under lawful DUI arrest as having consented to a blood test for drugs. If blood is unavailable, the person must take a urine test instead.
Also, an officer may ask a person who chose a breath test for blood when the officer has reasonable cause to believe drugs played a part. The officer must state those facts in the report.
Screening Versus Confirmation in DUI Toxicology Testing
A screening result may say a class of drug was present. Yet screens can react to related substances. Confirmation testing then checks for a specific drug and may report an amount.
- A screen suggests a possible presence
- A confirmation test identifies the specific substance
- Some reports give a concentration
Reading the report carefully avoids mistaking one stage for the other.
Detection Is Not Impairment
A positive DUI toxicology testing result shows a substance was present. However, it does not by itself show impairment at the time of driving. California has no general drug concentration limit like the 0.08 alcohol rule.
The article on drug detection versus impairment explains that difference. Prosecutors usually rely on other evidence too, such as driving behavior and a drug evaluation.
Medicine and Lawful Use
Some substances in a report may come from a valid prescription. Vehicle Code section 23630 says a legal right to use a drug under state law does not create a defense to a DUI charge. So lawful use does not end the inquiry.
The guide on prescription medication DUI questions covers that topic.
Records Worth Requesting
Ask for the full lab packet through discovery, since the summary sheet alone leaves out a lot. Then compare the methods, dates and analyst names. DUI toxicology testing records often include quality control data, which an expert can review. The article on DUI forensic expert reviews describes that work.