The Intox EC/IR II and the 15-Minute Observation Period: How NC Breath Tests Must Be Done

Breath testing · Intox EC/IR II

A North Carolina breath result is admissible only if the test was done the way the Department of Health and Human Services (DHHS) says it must be done, by an analyst holding a current permit for that instrument. In practice that means a 15-minute observation period before the sample, an accuracy check, at least two sequential breath samples that agree within 0.02, a machine that is on its four-month maintenance schedule, and a printed test record. Each of those steps leaves a trail, and each can be checked.

What G.S. 20-139.1(b) requires before a breath number comes in

North Carolina makes a breath result admissible without the usual scientific foundation, but only if two conditions are met: the test was performed under the DHHS rules, and the person who ran it held a current DHHS permit for that type of instrument. If either condition fails, the statutory shortcut is gone.

That bargain is written into G.S. 20-139.1(b). The legislature lets a valid result serve as “sufficient evidence to prove a person’s alcohol concentration,” and it tells judges to take notice of the DHHS rules and of the list of permits issued to analysts. In exchange, the State has to show the rules were actually followed. Those rules live in Subchapter 41B of Title 10A of the North Carolina Administrative Code, and for the Intox EC/IR II the most important ones are the definitions in .0101, the operating procedure in .0322 and the maintenance rule in .0323.

The 15-minute observation period, word by word

The observation period is a 15-minute window, immediately before the breath sample, during which a chemical analyst watches you to confirm you have not had anything to drink, eaten, smoked, vomited or regurgitated. It is both a waiting period and a watching period.

Some breath-testing programs talk about a “deprivation” period (nothing goes into the mouth) and an “observation” period (someone watches to be sure). North Carolina’s rule folds both ideas into one definition. The deprivation part is the list of five events: ingesting alcohol or other fluids, regurgitating, vomiting, eating and smoking. The observation part is the requirement that a chemical analyst, not just any officer, is the one watching. The timing part is that the 15 minutes must come immediately before the specimen is collected.

Two sentences in the rule are easy to miss and matter in court. The analyst may watch while working the instrument, so data entry does not have to come before the clock starts. And dentures, braces and oral jewelry stay in. The rule also says nothing about a minimum distance or about eye contact, which is why the case law focuses on whether the analyst was in a position to notice the five events.

Why it exists: mouth alcohol

A breath instrument is built to measure alcohol in deep-lung air. Alcohol sitting in the mouth or brought up from the stomach has not come from the lungs, and it can push a reading higher than the person’s true breath alcohol concentration.

North Carolina’s per se offense under G.S. 20-138.1(a)(2) is driving with an alcohol concentration of 0.08 or more, and G.S. 20-4.01(1b) lets that concentration be expressed in breath terms, as grams of alcohol per 210 liters of breath (results are reported to the hundredth and rounded down). The air at the end of a long exhale has been in contact with blood in the lungs, and its alcohol content tracks the blood. A sip of a drink, a wet burp or a little vomit adds alcohol to the mouth that never passed through the lungs. Residual mouth alcohol generally dissipates within minutes, which is the logic behind a short waiting period.

The eight steps of 10A NCAC 41B .0322

The Intox EC/IR II has its own operating rule. It applies to both the original model and the “Enhanced” model with serial number 10,000 or higher, and it lists eight steps in order.

1. Ensure the instrument displays the time and date

   The clock on the instrument becomes the clock on the test record, so later comparisons start here.

2. Ensure observation period requirements have been met

   The analyst confirms the observation requirements are being met. Because 41B .0101(6) lets the analyst keep observing while working the instrument, the full 15 minutes must be complete before the breath specimen is collected.

3. Initiate the breath test sequence

   The instrument runs its internal checks.

4. Enter information as prompted

   Names, permit number, agency and charge information.

5. Verify instrument accuracy

   The instrument tests a known control sample. Under 41B .0101(9), it must return the expected result or 0.01 less.

6. When “PLEASE BLOW” appears, collect a breath sample

   The first subject sample.

7. When “PLEASE BLOW” appears, collect a breath sample

   The second subject sample.

8. Print the test record

   The printed record documents each step and each result.

The rule adds two instructions. If the alcohol concentrations differ by more than 0.02, “a third or fourth breath sample shall be collected” when the instrument prompts for it. And sequential tests are given “as soon as feasible by repeating steps (1) through (8), as applicable.” Those two words, “as applicable,” have done a lot of work in the appellate cases discussed below.

Two sequential samples within 0.02

North Carolina requires at least two breath samples. If any two consecutively collected samples are within 0.02 of each other, the results are admissible, and only the lower of the two can be used to prove a particular alcohol concentration.

The requirement of two agreeing samples is itself a mouth-alcohol safeguard: residual alcohol in the mouth tends to produce a first result that the second does not match. It also creates a refusal trap. Under the same subsection, declining the second blow counts as a refusal, which carries its own civil revocation consequences, and the first number can still be used.

What counts as “sequential” has been litigated for decades. In State v. White (1987), two valid readings with two insufficient samples between them were still consecutive; a contrary rule would let a person defeat testing by blowing poorly. State v. Shockley (2009) applied the same reasoning on the older Intoxilyzer 5000. In State v. Cathcart (2013), an Intox EC/IR II timed out after an insufficient second blow and printed a ticket. The trooper reset the instrument, re-entered the data and got a second valid result 11 minutes after the first. The Court of Appeals held the tests were sequential, that it did not matter they printed on separate tickets, and that no new observation period was needed because the defendant had been watched continuously, about 51 minutes in all, with nothing going wrong.

The numbers in a North Carolina breath test

Every one of these requirements is checkable against a document. This table collects them in one place.

State v. Forney: the gum case

In State v. Forney (N.C. Ct. App. Jan. 16, 2024), the lead opinion of the Court of Appeals concluded that the observation rules were violated when an analyst took a second breath sample right after the driver spat out gum, without starting a new 15-minute period.

An Asheville officer saw the driver put mint gum in his mouth during the stop. At the jail, a permitted analyst completed a 15-minute observation period and took a first sample at 12:05 a.m. that read 0.11. He then learned about the gum, had the driver spit it out, and took a second sample at 12:07 a.m., also 0.11, without restarting the clock. The State argued that gum is not “eating.” The lead opinion said the trial court asked the wrong question: read literally, the list would allow lozenges, snuff or nicotine gum, an absurd result given the rule’s purpose. A new observation period was required.

The conviction still stood. Under G.S. 15A-1443(a), the defendant had to show a reasonable possibility of a different verdict without the error, and the court found the field sobriety results, red and glassy eyes, slurred speech and odor of alcohol were enough to convict on appreciable impairment. Two judges concurred only in the result, and one would have found no violation at all. So Forney shows that courts read the rule by its purpose, but it is not a settled rule about gum, and it shows the limits of winning the observation-period argument on appeal rather than before trial.

State v. Roberts: watching is not staring

The State must prove the observation period was met, but the analyst does not have to stare without blinking for 15 minutes. That is the two-part lesson of State v. Roberts, 767 S.E.2d 543 (N.C. Ct. App. 2014).

At the Pitt County Detention Center, a trooper began observing at 9:22 p.m. After the defendant put his fingers in his mouth, the trooper restarted the period at 9:52 p.m. At 10:06 p.m. he walked the defendant out to see whether a requested witness had arrived, and the defendant wiped his mouth on his jacket. The court relied on earlier cases, including State v. Drdak and State v. Gray, for the rule that the State bears the burden of proving compliance. But it held the regulation does not require the analyst to stare in an unwavering manner; the trooper stayed with the defendant both times they left the room, and “split second” lapses did not show a violation. The court noted the 2001 amendment letting one analyst observe more than one person, which would make no sense if constant staring were required. The testing-room camera in Roberts was motion-activated, so its timestamps did not reflect real elapsed time, a reminder that video must be examined carefully.

Strict rules, practical reading: how compliance is judged

North Carolina’s statute asks whether the test was performed “in accordance with” the DHHS rules. The appellate cases read those rules by their text and purpose, in both directions: technical departures that do not touch the rule’s purpose have been excused, and departures that defeat its purpose have not.

On the State’s side of the ledger, State v. Moore, 132 N.C. App. 802 (1999), held that not all eight steps have to be repeated for a later test, because the rule says to repeat them “as applicable,” and Cathcart applied that reasoning to excuse a new observation period after a machine reset. Roberts refused to read “observes” as “stares.” On the defense side, the lead opinion in Forney refused to read the list of five events so literally that it would let something in the mouth slip by. The burden also differs by issue: the State must prove the observation period, while under G.S. 20-139.1(b2) the defendant must object and show that preventive maintenance was not done on time.

Permits: who is allowed to run the test

Only a “permittee,” a chemical analyst holding a valid DHHS permit for the type of analysis performed, can give an admissible test. The permit must be current on the day of the test and must cover the instrument used.

G.S. 20-139.1(b) lets DHHS issue permits “subject to periodic renewal, termination, and revocation,” and it requires the court to take judicial notice of the list of permits, the instrument type and the date issued. The DHHS Forensic Tests for Alcohol Branch posts individual certification and permit-history reports on its maintenance and permit history page. Compare the permit number printed on the test record with that history. A lapsed permit is uncommon, but it is a clean issue when it happens.

Maintenance records and the accuracy check

Each Intox EC/IR II must receive preventive maintenance at least once every four months under 10A NCAC 41B .0323, and the signed record must be kept at DHHS for three years. A result is excluded for late maintenance only if the defendant objects and shows the maintenance was not done in time.

The maintenance routine checks the ethanol gas canister pressure or simulator temperature, confirms the date and time, runs a test sequence with an accuracy check and prints a record, and runs a diagnostic that must show a passing status. The posted maintenance histories are monthly reports listed by year and month, and the instrument serial number printed on your test record is what ties a test to the right maintenance entry. The courts must take judicial notice of the maintenance records under G.S. 20-139.1(b2), which cuts both ways: the records are easy to use, and a vague claim that the machine “might” have been off goes nowhere. In State v. Simmons, 205 N.C. App. 509 (2010), a maintenance challenge failed because the required step had been done 23 days before the test.

The accuracy check during each test is separate. The instrument analyzes a control sample, and under 41B .0101(9) it must return the expected result or 0.01 less. The Supreme Court of North Carolina explained in State v. Shuping, 312 N.C. 421 (1984), that this kind of tolerance is not a margin of error in the subject’s result. Because the allowed deviation runs only below the expected value, an instrument at the edge of tolerance is reading low, so any error favors the person tested.

The software and the printout

The test record is the instrument’s own account of what happened. It shows the instrument serial number, date and times, the internal checks, the accuracy check, each subject sample and the reported result, plus the analyst’s name and permit number.

Read it against the rules. Does the first sample time come at least 15 minutes after the observation start the officer recorded? Did anything happen in the room after that start? Is the reported number the lower of the two agreeing samples? If there were insufficient samples or a reset, is there a second ticket, as in Cathcart? Field labels and layout can vary with the instrument’s software version, so compare line by line rather than against someone else’s ticket. Our guide to NC breath-testing records lists what to request, and the breath-test timeline case study shows how the times fit together.

Two procedural points. In district court the State may offer the analyst’s affidavit instead of live testimony if it gives notice and a copy at least 15 business days before the proceeding, and the defense waives the objection unless it files one at least five business days before (G.S. 20-139.1(e1)–(e2)). And the U.S. Supreme Court held in California v. Trombetta that due process does not require police to preserve breath samples, because defendants can attack calibration, interference and operator error by other means. That makes the paper and video record, not a retained sample, the place to look.

Key cases on breath-test procedure

These are the decisions that frame breath-test procedure arguments in North Carolina courts. Our breath-testing case law page and the full NC DWI case law library collect more.

The observation period is fifteen minutes long, but the argument about it can decide whether a jury ever sees the number.Adkins & Purkey

What happens if a rule was not followed

The usual remedy is suppression of the breath result, not dismissal of the charge. Without an admissible number, the State loses the per se route under G.S. 20-138.1(a)(2) and must prove appreciable impairment with other evidence.

In district court, motions to suppress generally must be made before trial under G.S. 20-38.6. Excluding the number also matters at sentencing, because an alcohol concentration of 0.15 or more is an aggravating factor under G.S. 20-179 and affects ignition interlock. Be realistic: as Forney shows, a strong appreciable-impairment case can survive, and the separate 30-day civil revocation has its own process. How much a procedure issue is worth depends on the rest of the evidence, which is why it belongs in a full evidence review and the plea-or-trial decision.

Quiz: how well do you know the breath-test rules?

• Write down whether you ate, drank, chewed gum, smoked, burped or vomited after the stop.
• Note when your rights were read and when the officer said observation began.
• Keep your test record and rights form.
• Note whether the analyst left the room or took you out of it.
• Ask a lawyer to request preservation of testing-room and body-camera video quickly.
• Bring everything to your consultation.

Top 10 FAQs: the breath test observation period

General North Carolina legal information as of November 2026, not legal advice for any specific case. Reading this article does not create an attorney-client relationship. Attorney advertising.