DUI blood samples in Montana are analyzed by the State Crime Lab, formally the Forensic Science Division of the Department of Justice, and the result comes back as a toxicology report listing each substance found and its amount. The report is evidence, not a verdict. It has to come from a qualifying laboratory, it has to be read against the exact words of the statute, and a person from the lab generally has to testify before it is used at trial. This page is part of our Montana DUI Guide.
What the State Crime Lab Is
State law establishes "a laboratory of criminalistics within the department of justice" to analyze specimens submitted by Montana law enforcement officers and state agencies, including toxicologic specimens (MCA § 44-3-301(1), (2)). The administrative rules for alcohol and drug testing define "the laboratory" as the Forensic Science Division (ARM 23.4.201(18)). The same statute directs the laboratory to establish a Yellowstone County branch, with priority given "to the relief of the backlogs of chemistry and toxicology statewide" (MCA § 44-3-301(3)).
The Division does more than test blood. It approves breath instruments, certifies breath test operators, and supplies the blood collection kits officers use (ARM 23.4.212, 23.4.216, 23.4.220(5)).
Which Laboratories Count
A report of a blood test is admissible if the sample "was analyzed in a laboratory operated or certified by the department or in a laboratory exempt from certification under the rules of the department," and the blood was drawn by a person competent to do so (MCA § 61-8-1018(1)(b)(ii)).
Exempt laboratories are clinical and hospital laboratories under the direct supervision of a pathologist or certified medical technologist that hold the license or accreditation the rule describes (ARM 23.4.203). That is how a hospital's own result can end up in a DUI case, a subject covered in hospital blood tests after a crash.
From the Draw to the Report
The sample arrives at the lab in a sealed, labeled tube from a Division kit, with a request form. The rules require the tube to carry the subject's name, the date and time of collection, and a signed and dated evidence seal (ARM 23.4.220(3)). A sample without enough volume "will not be analyzed" (ARM 23.4.220(4)). The rules also say a test of a blood sample "may consist of more than one analysis" under the Division's procedures (ARM 23.4.201(25)).
Every transfer between the person who drew the blood, the officer, the evidence room, and the analyst should be documented. That record is the chain of custody. How the draw itself must be done is in blood test procedure.
How to Read a Toxicology Report
Formats change, so read your own report for three things: the substance named, the amount, and the unit. Then compare each line to the statute.
| Finding | Statutory unit | What it is compared to | MCA |
|---|---|---|---|
| Alcohol (ethanol) | Grams of alcohol per 100 milliliters of blood | 0.08, 0.04 commercial, 0.02 under 21; 0.16 for aggravated DUI | §§ 61-8-1001(1), (3), 61-8-1002(1) |
| Delta-9-THC | Nanograms per milliliter of blood | 5 ng/mL, excluding inactive metabolites. Any amount for a driver under 21 | § 61-8-1002(1)(d), (e)(ii) |
| Listed drugs | Nanograms per milliliter of blood | For example fentanyl 0.5, methamphetamine 20, amphetamine 20, cocaine 20, without a valid prescription | § 61-8-1002(1)(f) |
| Any other drug | Reported as detected or as an amount | No per se number. Relevant only to an impairment charge, with other competent evidence | § 61-8-1018(1)(a) |
A few reading points come straight from the rules and statutes:
- What was tested. The rules define "blood" to include whole blood, serum, or plasma (ARM 23.4.201(6)). The report or the lab file should say which. It is a fair question for the analyst.
- Metabolites. The THC limit excludes inactive metabolites. The listed drug limits, by contrast, name some metabolites on purpose, such as cocaine metabolite and the heroin metabolites morphine and 6-monoacetyl morphine.
- Prescriptions. The listed drug limits apply to a person "without a valid prescription."
- Time. The report describes the blood at the moment of the draw. The collection time on the tube, compared with the time of driving, matters for alcohol in particular (MCA § 61-8-1002(2)).
The full list of drug limits is in Montana drug per se limits.
What the Report Does Not Prove
A number at or above a per se limit proves that element of a per se charge if the test is reliable. For an impairment charge based on drugs, the statute is explicit that "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," and that other competent evidence is required (MCA § 61-8-1018(1)(a)). A report listing a prescribed medication at some level is the beginning of that analysis, not the end. See prescription and drug DUI.
Turnaround and Delay
We looked for a deadline by which the lab must report a DUI result and did not find one in the statutes or rules cited on this page. The Department of Justice's DUI manual for prosecutors, in a passage about subpoenas, tells its readers that "the Crime Lab is understaffed and swamped." That is the State's own description, from a manual last revised in 2024.
Delay has consequences on both sides. A person can wait a long time under a charge without knowing the evidence. And a misdemeanor must generally be brought to trial within 6 months after the plea unless the defendant postponed it or the State shows good cause (MCA § 46-13-401(2)). Whether lab delay counts as good cause depends on the facts.
The Analyst at Trial
The Sixth Amendment gives an accused person the right to confront the witnesses against them. In Melendez-Diaz v. Massachusetts (2009), the United States Supreme Court held that sworn laboratory certificates were testimonial statements and that admitting them without the analysts violated that right. In Smith v. Arizona (2024), the Court held that when a substitute expert conveys an absent analyst's statements in support of an opinion, and the statements support that opinion only if true, they come into evidence for their truth. That raises the same confrontation problem.
Montana practice follows. The Department of Justice's prosecutor manual states that blood results require expert testimony and that the State "must call" the toxicologist, or hospital laboratory scientist, who tested the blood. It also advises prosecutors to give written notice before offering crime lab records, with enough time for the defense to prepare.
For the defense, the analyst's testimony is an opportunity to ask what method was used, what was actually measured, how the instrument was checked that day, and how certain the reported amount is. Those questions, and the option of an independent analysis, are discussed in challenging the blood test.
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. It is not legal advice about your specific case.