Oral Fluid (Saliva) Testing in Montana DUI Law

Oral fluid testing exists in current Montana DUI law. A person who drives here is considered to have consented to a test of blood, breath, or oral fluid, and the evidence statute makes oral fluid results admissible on stated conditions. What the law does not yet supply is the kind of detailed procedure and case law that surrounds breath and blood tests. This page sets out what is written down and what is still open. It is part of our Montana DUI Guide.

Where Oral Fluid Appears in the Statutes

The Montana Department of Justice's DUI manual for prosecutors notes that a 2023 law, Senate Bill 13, returned oral fluid testing to the DUI statutes. We read each of the following sections in the current code on October 9, 2026.

Screening Versus Proof

The evidence statute groups the "oral fluid screening test" with the breath test and the roadside preliminary alcohol screening test, and it applies the same condition to all three: the test must have been performed by a person certified by the Forensic Science Division to administer it (MCA § 61-8-1018(1)(b)(i)). Blood is handled in a separate clause that looks at the laboratory and the person who drew the sample.

The word "screening" is the statute's own. A screening test is generally a first look that tells an officer which direction to investigate. The statute does not say how much weight a screening result carries, and it does not describe a separate laboratory confirmation step for oral fluid. If an oral fluid result is part of your case, the first questions are what kind of test it was, who gave it, and whether a blood sample was also taken.

What an Oral Fluid Result Cannot Do Alone

For a drug-based impairment charge, the Legislature wrote a limit directly into the statute. Evidence of a drug shown by analysis of blood, breath, or oral fluid is admissible, but "a positive test result does not, in itself, prove that the person was under the influence of a drug or drugs at the time the person was in control of a vehicle." A person may not be convicted of an impairment DUI based on the presence of a drug "unless some other competent evidence exists that tends to establish that the person was under the influence" (MCA § 61-8-1018(1)(a)).

That other evidence usually comes from the driving, the officer's observations, the field sobriety tests, and sometimes an evaluation by a drug recognition expert.

The Per Se Drug Limits Are Written for Blood

Montana has two kinds of drug limits that do not require proof of impairment. The wording of each matters for oral fluid:

• THC. The limit is 5 ng/mL, excluding inactive metabolites, "as shown by analysis of the person's blood or other bodily substance" (MCA § 61-8-1002(1)(d)). Oral fluid is not named, although "other bodily substance" is broad.
• Listed drugs. The limits for amphetamine, cocaine, heroin, LSD, methamphetamine, PCP, fentanyl, and the listed metabolites apply to amounts "as shown by analysis of the person's blood" (MCA § 61-8-1002(1)(f)). No other sample is mentioned.

Reading those two subsections side by side, a charge under the listed drug limits depends on a blood result. Whether an oral fluid number could support the THC limit is not something we found answered in a Montana Supreme Court decision. Our pages on THC DUI and prescription and drug DUI cover those charges.

Oral Fluid and Alcohol

The alcohol limits name oral fluid as one way an alcohol concentration may be shown. At the same time, the definition of "alcohol concentration" in MCA § 61-8-1001(3) is stated only as grams of alcohol per 100 milliliters of blood or per 210 liters of breath. The statutes we read do not explain how an oral fluid measurement would be expressed in either unit. That is a gap in the text, and we point it out without predicting how a court would resolve it.

What the Rules and the Courts Have Not Yet Covered

The Department of Justice is directed to adopt uniform rules for giving tests (MCA § 61-8-1019(5)). Its rules in ARM Title 23, chapter 4, subchapter 2 deal in detail with breath instruments, operator permits, field certification, and blood collection. We read every rule currently in effect in that subchapter and found none that addresses how an oral fluid sample is collected, what device is approved, or how an oral fluid operator is certified. The general definition of a "sample" does reach any biological fluid (ARM 23.4.201(23)).

The courts are in a similar place. The Department of Justice's prosecutor manual says that the rules for admitting oral fluid tests "have not been addressed by the Montana Supreme Court" and that it anticipates foundational requirements similar to blood testing, including expert testimony. That statement is from a manual last revised in 2024, and we did not find a later decision that changes it.

If You Were Asked for an Oral Fluid Sample

• Write down what the officer said about the test, what device was used, and whether you were shown a result.
• Note whether a blood draw followed, and where.
• Keep any prescription information for medication you take. A valid prescription matters under the listed drug limits.
• Remember that the refusal rules are the same for every kind of test. If your license was taken, the 30-day window to petition is running.

Because this area is new, the certification of the person who gave the test and the documentation of the device are the first records to request. On request, full information about any test given at an officer's direction must be made available to you or your attorney (MCA § 61-8-1019(3)). For the blood side of a drug case, see the crime lab and toxicology reports.

This page explains Montana law in general as of the 2025 Montana Code Annotated and the Administrative Rules of Montana in effect on October 9, 2026. Oral fluid testing is a developing area and the rules may change. It is not legal advice about your specific case.