Challenging DUI Breath and Blood Tests in Nevada: What Every Las Vegas Defendant Needs to Know

Nevada DUI convictions frequently depend on breath or blood test results. Those results are not unassailable. Here is how experienced criminal defense attorneys challenge the evidence in court.

Why DUI Test Evidence Is Not Self-Proving

Nevada DUI prosecutions typically rely on one of two forms of chemical test evidence: a breath test administered roadside or at a police station, or a blood draw typically conducted at a medical facility under a warrant. Both forms of evidence appear authoritative in court, but both are subject to challenge based on procedural, technical, and scientific grounds that a skilled defense attorney investigates in every case.

The broader significance of challenging test evidence has increased under Nevada's 2026 sentencing changes. For DUI causing death, the maximum sentence is now 25 years. For ordinary DUI charges involving injury or repeat offenses, the 2026 changes similarly increased penalties. The higher the stakes of a conviction, the more important it becomes to rigorously examine every link in the prosecution's evidence chain.

A challenge to test evidence does not require proving the machine was wrong or that the officer lied. It requires identifying procedural or scientific problems that create reasonable doubt about whether the test result accurately reflects the defendant's impairment at the time of the alleged offense. Those problems exist more often than the prosecution's presentation suggests.

Breath Test Challenges: Calibration, Certification, and Timing

Evidentiary breath testing machines used in Nevada DUI cases, most commonly the Intoxilyzer series, must be calibrated and maintained according to specific protocols, with records of that maintenance available for defense review. A machine that has not been properly calibrated within the required interval, or that has documented calibration errors, produces results whose accuracy cannot be certified.

The administering officer must also hold current certification to operate the specific device used. Certification lapses, improper administration procedures, and failure to observe the required deprivation period before testing, during which the subject must not eat, drink, burp, or introduce any substance into the mouth, can all affect the admissibility or weight of the test result.

Timing also matters. Nevada DUI law provides specific windows within which a breath or blood test must be administered to be considered presumptively accurate for the time of driving. A test taken significantly later than the alleged time of impaired driving introduces scientific uncertainty about what the BAC was when the vehicle was being operated, because alcohol is metabolized over time at rates that vary by individual.

Blood Test Challenges: Chain of Custody and Laboratory Procedures

Blood draw evidence in Nevada DUI cases must be collected by qualified personnel, stored in properly sealed containers with appropriate preservatives, and maintained in a documented chain of custody from the collection site through the testing laboratory and through the courtroom. Any gap in that documentation creates a question about whether the sample analyzed in the lab is the same sample drawn from the defendant.

Laboratory analysis procedures are also subject to challenge. The lab must use approved testing methods, maintain its equipment according to applicable standards, and have qualified analysts perform and certify the results. Defense attorneys can request the full laboratory analysis records, including any quality control runs performed on the day of analysis, to identify procedural deviations.

The blood sample itself is also subject to independent retesting in most cases. Nevada law provides defendants with the right to obtain a portion of the sample for independent analysis. When a defense laboratory's analysis produces a result that differs from the prosecution's, that discrepancy becomes powerful evidence of reasonable doubt.

Why the Defense Analysis Must Begin Immediately

Breath test records, including calibration logs and officer certification documents, must be requested promptly through formal discovery. Some records are retained for limited periods, and delays in making discovery requests can result in documents no longer being available. Blood samples deteriorate over time, and the opportunity for independent retesting may be lost if not pursued while the sample is still viable.

An experienced Nevada criminal defense attorney begins the evidence review process immediately upon retention, which is one of the primary reasons early legal representation matters in DUI cases. Waiting until the first court date to engage an attorney means losing weeks during which evidence could have been reviewed, experts could have been consulted, and defense strategies could have been evaluated.

Freedom First Criminal Defense provides free, confidential consultations for individuals facing DUI charges in Las Vegas and throughout Nevada. If you or someone you care about has been charged with DUI, contact us before the first court appearance. The sooner an attorney is involved, the more options remain available.

6 DUI Evidence Problems That an Experienced Defense Attorney Investigates

Prosecutors present breath and blood test results as straightforward facts. They are not. Here are six categories of problems that defense attorneys investigate in every Nevada DUI case:

1. Breath machine calibration records: The machine used must be calibrated within specified intervals, with complete records available. A calibration gap or a documented calibration error is a direct challenge to the test's accuracy.
2. Officer certification for the specific device: Each model of evidentiary breath testing device requires specific officer certification. An officer who used a device for which their certification has lapsed administered an unauthorized test.
3. Deprivation period compliance: Before administering a breath test, the officer must observe the subject for a required period to ensure no substances enter the mouth. Failure to document this observation creates an admissibility challenge.
4. Test timing relative to the time of driving: A test taken long after the driving event introduces scientific uncertainty about the BAC at the time of the alleged offense, because alcohol is metabolized over time at variable rates.
5. Blood sample chain of custody: Every transfer of a blood sample from collection through laboratory analysis must be documented. A gap in the chain is a challenge to whether the analyzed sample is the same sample collected from the defendant.
6. Laboratory quality control records: The laboratory's quality control runs on the day of analysis, the analyst's qualifications, and the approved method used for analysis are all reviewable and potentially challengeable.

Frequently asked questions

If I refused a breath test, does that help my defense?

Refusal to take a breath test in Nevada triggers an automatic license suspension and can be used as evidence of consciousness of guilt at trial. However, it also means the prosecution lacks the primary chemical evidence, which changes the nature of the case. An attorney can evaluate the specific consequences of a refusal in your situation.

Can my defense attorney request the calibration records for the breath machine?

Yes. Calibration records, maintenance logs, and officer certification documents are all subject to formal discovery requests in a criminal case. Obtaining them is a standard step in DUI defense investigation.

What if I agreed to a blood test -- can I still challenge the results?

Yes. Chain-of-custody problems, laboratory procedure deviations, and the right to independent retesting are all available regardless of whether the defendant consented to the draw.

Is Freedom First Criminal Defense available for a free consultation?

Yes. All consultations are free and confidential, with no obligation to retain us. Call us any time in Las Vegas.