Challenging Breath Test Evidence in a New Jersey DWI Case

 A breath-test reading can become some of the most important evidence in a New Jersey DWI prosecution. If the State intends to rely on a reported blood alcohol concentration, however, the number produced by an Alcotest machine should not simply be accepted at face value.

New Jersey requires breath testing to be performed with approved equipment, by a qualified operator, and in accordance with procedures designed to produce a reliable result. Problems involving the machine, calibration records, observation period, testing procedure, foundational documents, or the circumstances surrounding the breath samples may become important defense issues.

A DWI defense attorney should therefore examine how the breath test was administered, whether the State can establish the required foundation for admission, and whether the machine and its supporting records were reliable in the particular case.

For a broader overview of New Jersey DWI law, penalties, testing issues, and defenses, visit our New Jersey DWI Lawyer and Defense Guide.

How Breath Testing Is Used in a New Jersey DWI Case

New Jersey’s DWI statute, N.J.S.A. 39:4-50, permits prosecution based on a prohibited blood alcohol concentration as well as other evidence of intoxication.

When police obtain an admissible breath-test result, the State may rely on the reported BAC as direct evidence of a per se DWI violation.

That makes the reliability and admissibility of the breath test critically important.

The defense should determine not only what number appears on the Alcohol Influence Report, but also whether the State can establish that the testing process leading to that number complied with New Jersey law.

New Jersey’s Implied-Consent Law

Under N.J.S.A. 39:4-50.2, a person who operates a motor vehicle on a public roadway or qualifying quasi-public area in New Jersey is deemed to have consented to breath testing when police have reasonable grounds to believe the person operated in violation of New Jersey’s DWI law.

The statute also provides that the person tested may obtain an independent chemical test by a person or physician of their own selection.

Refusing the required breath samples can lead to a separate refusal prosecution under N.J.S.A. 39:4-50.4a.

Breath-test refusal and a challenge to the accuracy of an actual breath-test result are therefore separate legal issues.

State v. Chun and the Alcotest 7110

The major New Jersey Supreme Court decision governing the Alcotest 7110 is:

State v. Chun, 194 N.J. 54, 943 A.2d 114 (2008), cert. denied, 555 U.S. 825 (2008).

In Chun, the New Jersey Supreme Court conducted an extensive review of the Alcotest 7110 MKIII-C and concluded that the device was sufficiently scientifically reliable for use in New Jersey DWI prosecutions when operated in accordance with the safeguards imposed by the Court.

The significance of Chun is not simply that the machine was approved.

It established a framework requiring the State to demonstrate that the particular test was performed properly and supported by the necessary foundational evidence.

The Alcotest instruments used in New Jersey are manufactured by Dräger, whose name also appears throughout the technical manuals and foundational records associated with breath testing. A defendant reviewing a discovery packet may therefore see references to “Dräger,” “Draeger,” or the specific Alcotest model even when the documents are discussing the same breath-testing system. New Jersey court records specifically refer to the “Drager New Jersey State Police User Manual” for the Alcotest 7110 MKIII-C.

What Must the State Establish for an Alcotest Result?

The State generally must establish that:

• the Alcotest instrument was in proper working order;
• the operator was properly certified;
• required procedures were followed;
• the instrument was properly calibrated;
• required control and simulator checks were satisfied; and
• the breath samples themselves were obtained in accordance with applicable procedures.

The defense should review the State’s documents rather than assume those conditions were satisfied merely because the machine produced a numerical reading.

The 20-Minute Observation Period

One of the most important procedural safeguards is the pre-test observation period.

Before breath samples are taken, the operator generally must continuously observe the defendant for at least 20 minutes.

The purpose is to ensure that something does not occur that could interfere with the breath sample, such as:

• eating;
• drinking;
• smoking;
• vomiting;
• regurgitation; or
• placing a foreign substance in the mouth.

New Jersey appellate decisions applying Chun regularly discuss the required 20-minute observation period as part of the breath-test foundation.

The defense should therefore determine when the observation period actually began, who conducted it, whether the officer continuously observed the defendant, and whether anything occurred that should have restarted the period.

Learn What Can Go Wrong During the 20-Minute Observation Period

The police report may simply state that the defendant was “observed for 20 minutes.” That does not necessarily establish what actually occurred during the observation period.

The defense should examine:

• Whether the officer documented the start and end times
• Whether the officer left the room during the observation period
• Whether multiple officers supposedly shared the observation
• Whether the officer was completing paperwork or performing other tasks at the same time
• Whether body-camera or station video shows continuous observation
• Whether the driver belched, vomited, or regurgitated
• Whether the driver ate, drank, smoked, or placed anything in the mouth
• Whether an event occurred that should have restarted the observation period

A police report stating that a 20-minute observation occurred is not the same as objective proof that the required observation was actually completed. Where video exists, the timeline should be compared against the written Alcotest documentation.

Calibration Records and State v. Cassidy

Breath-testing equipment must be properly calibrated.

The importance of calibration was highlighted by the New Jersey Supreme Court in:

State v. Cassidy, 235 N.J. 482, 197 A.3d 86 (2018).

The case arose after State Police coordinator Marc Dennis falsified calibration records involving Alcotest instruments.

The Supreme Court adopted the Special Master’s findings and held that breath-test results from Alcotest instruments that had not been calibrated using a thermometer traceable to standards of the National Institute of Standards and Technology were inadmissible.

Cassidy demonstrates an important principle:

A breath-testing device does not become reliable merely because it is an approved model. The State must be able to establish that the particular instrument was maintained and calibrated in accordance with required procedures.

Why Cassidy Still Matters

The facts of Cassidy involved extraordinary calibration misconduct, but the case remains important because it illustrates why supporting records matter.

A defense attorney should determine:

• which instrument performed the test;
• when that instrument was calibrated;
• who performed the calibration;
• whether the coordinator was properly certified;
• whether required equipment was used;
• and whether the calibration documentation is complete and internally consistent.

The Appellate Division later recognized the continuing consequences of Cassidy in State v. Zingis, where a prior DWI sentence could not be enhanced without proof that the prior conviction was not based on an Alcotest result rendered inadmissible under Cassidy.

What Alcotest Documents Should Be Reviewed?

A breath-test defense often depends heavily on discovery.

Records commonly associated with an Alcotest prosecution can include:

• the Alcohol Influence Report;
• operator certification;
• calibration records;
• coordinator certification;
• simulator-solution documentation;
• certificates of analysis;
• instrument inspection records;
• and other foundational documents required for the particular device.

The exact documents that matter can depend on the Alcotest model and the facts of the case.

The defense should compare the dates, serial numbers, certifications, control results, and other information rather than merely confirming that documents were produced.

For broader discussion of documentary and scientific evidence review, see our Chain of Custody & Evidence Audits in New Jersey.

Learn What a Simulator Solution is and Why it Matters

An Alcotest does not simply accept a driver’s breath and display a number without internal quality-control procedures.

A simulator solution is a liquid alcohol reference solution with a known alcohol concentration that is heated in a simulator device to produce an alcohol vapor of a known value. The Alcotest analyzes that vapor as a quality-control check before and after the defendant’s breath tests to confirm that the instrument is producing a reading within the required range before or during breath testing. Simulator solutions are used as part of the testing and calibration system to help determine whether the instrument is measuring within required tolerances. The simulator solution is produced by the manufacturer, Draegar, to test against its own machines

The defense should examine whether:

• The correct simulator solution was used
• The solution was changed when required
• The solution was supported by the required certification
• The control readings fell within permitted tolerances
• The solution lot information matches the supporting records
• The documentation corresponds to the Alcotest instrument used in the defendant’s case
• The relevant dates and serial numbers are internally consistent

Problems with the supporting control process may raise questions about whether the State can establish the required foundation for the reported breath-test result.

The Alcotest 9510 in New Jersey

New Jersey has been transitioning from the Alcotest 7110 MKIII-C to the newer Alcotest 9510.

That development creates an important distinction for current DWI cases.

In 2023, the New Jersey Supreme Court granted direct certification in State v. Colleen A. Cunningham, A-38-22 (087913) to address whether results produced by the Alcotest 9510 were sufficiently scientifically reliable for use in DWI cases. The Court also imposed a limited statewide stay involving certain 9510 prosecutions.

That proceeding never resulted in a Supreme Court decision declaring the 9510 scientifically reliable.

In December 2025, Cunningham withdrew her challenge. Because there was no longer a party pursuing the scientific-reliability issue, the Supreme Court dismissed the proceeding and lifted the statewide stay.

The Court specifically stated that prosecutions relying on the Alcotest 9510 could proceed and that individual defendants remain free to challenge the scientific reliability of the 9510 in their own cases.

That is the current procedural posture and should not be confused with a Supreme Court merits decision approving the 9510.

Why the 7110 and 9510 Should Not Be Treated as Identical

State v. Chun addressed the scientific reliability of the Alcotest 7110 MKIII-C.

The Alcotest 9510 is a different instrument.

Therefore, in a current New Jersey DWI case, one of the first questions should be:

Which Alcotest model actually generated the defendant’s breath-test result?

That can affect the governing legal and scientific issues.

Learn if the Alcotest 9510 Can Still Be Challenged

Yes. The dismissal of the statewide Alcotest 9510 proceeding in State v. Cunningham did not result in a New Jersey Supreme Court decision resolving the scientific reliability of the Alcotest 9510 on the merits.

The Supreme Court lifted the statewide stay after the defendant withdrew her challenge, but expressly recognized that individual defendants may still raise scientific-reliability challenges to the Alcotest 9510 in appropriate cases.

That makes it important to determine exactly which breath-testing machine was used in the defendant’s case.

State v. Chun, 194 N.J. 54, 943 A.2d 114 (2008) addressed the Alcotest 7110 MKIII-C. The Alcotest 9510 is a different instrument and should not automatically be treated as though the two devices have identical legal and scientific histories.

Whether a reliability challenge to the 9510 is appropriate depends on the facts of the particular case, the available scientific evidence, and the legal issues presented.

Operator Certification and Proper Administration

A properly functioning machine can still produce evidence that is challenged if the operator did not follow required procedures.

The defense should review:

• the operator’s certification;
• whether certification was current;
• the testing sequence;
• the observation period;
• whether the defendant provided acceptable breath samples;
• any error messages;
• any aborted or repeated attempts;
• and the final Alcohol Influence Report.

Where video exists inside the police station, it can also be compared with the written Alcotest paperwork.

What If There Were Error Messages or Multiple Breath Attempts?

Alcotest records may contain information beyond the final BAC number.

Depending on the test, the machine may record:

• insufficient volume;
• insufficient duration;
• interference;
• invalid samples;
• aborted tests;
• repeated attempts;
• or other status information.

Those entries should be reviewed in context.

An error message does not necessarily mean the final test is automatically inadmissible, but it can reveal what occurred during the testing sequence and whether additional investigation is warranted.

Learn How Mouth Alcohol Affect a Breath Test?

Breath-testing procedures are designed in part to reduce the risk that residual alcohol in the mouth will interfere with the accuracy of a breath sample.

That is one of the reasons New Jersey requires an observation period before breath samples are taken.

Potential issues can include:

• Vomiting
• Regurgitation
• Recent drinking
• Food or another substance placed in the mouth
• Smoking
• Other events occurring during the observation period

If an event occurs that could introduce alcohol or another substance into the mouth, the defense should examine whether the officer recognized the event and whether the required observation procedure was restarted.

Police reports, Alcotest times, body-camera footage, station video, and the defendant’s recollection can all become relevant when evaluating what happened before the breath samples were obtained.

Mouth Alcohol, Acid Reflux, GERD, and Belching

The Alcotest is intended to measure alcohol in deep-lung breath, not alcohol remaining in the mouth. Residual alcohol in the mouth can therefore become important if something occurs shortly before testing that introduces alcohol-containing vapor into the oral cavity.

That is one reason New Jersey requires the 20-minute observation period. Courts have specifically described the observation period as a safeguard against contamination from events such as vomiting or regurgitation before the breath samples are taken.

Conditions or events worth investigating can include gastroesophageal reflux disease (GERD), acid reflux, belching, regurgitation, vomiting, recent drinking, and certain dental appliances or dentures when the facts suggest they may have retained or reintroduced alcohol into the mouth.

The important question is not simply whether a defendant has GERD or wears dentures. The defense must determine whether there is evidence that mouth alcohol may actually have been present during the testing sequence and whether the officer’s observation adequately addressed that risk.

Can Medical Conditions Affect Breath Testing?

Certain medical issues may become relevant depending on the facts of the case.

For example, a defense investigation may consider whether the person experienced:

• vomiting;
• regurgitation;
• gastrointestinal problems;
• respiratory limitations;
• difficulty producing an adequate breath sample;
• or another condition that affected the testing process.

Medical conditions should not be raised merely because they are theoretically capable of affecting a test.

The question is whether there is actual evidence connecting the condition to what happened during this defendant’s breath test.

We will address those issues in more depth on our separate medical conditions and New Jersey DWI defense page.

Breath Testing and Police Video

Body-camera or stationhouse video can sometimes provide important evidence concerning the breath-testing process.

Video may help determine:

• when the defendant arrived at the station;
• when the observation period began;
• who was actually observing the defendant;
• whether the officer left the room;
• whether the defendant ate, drank, vomited, or placed something in their mouth;
• whether the defendant had difficulty breathing;
• whether instructions were properly given;
• and whether the times in the paperwork match what occurred.

Police documentation should be compared with objective recordings whenever those recordings exist.

For more information about using video to evaluate police reports, see our body-camera footage defense guide.

Can an Alcotest Result Be Suppressed?

Potentially.

Whether a breath-test result can be excluded depends on the nature of the defect and whether the State can establish the legal and scientific foundation required for admission.

Potential issues can include:

• unlawful police conduct before the breath test;
• failure to satisfy foundational requirements;
• improper calibration;
• deficient observation procedures;
• operator problems;
• discovery showing inconsistencies in the testing process; or
• a scientific challenge to the instrument itself where legally appropriate.

These issues may be litigated through pretrial motions and evidentiary hearings.

See our guide to motions to suppress evidence in New Jersey.

Breath-Test Evidence Does Not Exist in Isolation

Even where a breath result is challenged, the defense should evaluate the rest of the DWI evidence.

That may include:

• driving behavior;
• observations made during the traffic stop;
• field sobriety testing;
• statements;
• body-camera footage;
• proof of operation;
• and other circumstantial evidence.

Likewise, a strong breath-test result does not eliminate the need to determine whether the original DWI traffic stop was lawful or whether the field sobriety tests were properly administered.

What A DWI Defense Attorney Should Review

A thorough breath-test review may include:

• Alcotest model
• Alcotest serial number
• Alcohol Influence Report
• BAC results
• operator certification
• calibration documents
• coordinator certification
• simulator-solution records
• certificates of analysis
• observation-period timing
• police reports
• body-camera or station video
• error messages
• incomplete or repeated breath attempts
• medical issues
• discovery inconsistencies
• whether the test involved an Alcotest 7110 or 9510
• whether the State can establish the foundation required for admission

The focus should always be on the particular machine, particular operator, particular test, and particular defendant.

Frequently Asked Questions About New Jersey Breath Tests

What breath-testing machine does New Jersey use for DWI cases?

New Jersey historically relied heavily on the Alcotest 7110 MKIII-C and has been transitioning to the newer Alcotest 9510. Which machine was used can matter because the legal history surrounding the two instruments is different.

What is State v. Chun?

State v. Chun, 194 N.J. 54, (2008) is the leading New Jersey Supreme Court decision concerning the scientific reliability and admissibility of the Alcotest 7110.

Is there a required observation period before an Alcotest?

Yes. New Jersey requires a 20-minute observation period before breath testing under the procedures developed through Chun and subsequent Alcotest cases.

What is State v. Cassidy?

State v. Cassidy, 235 N.J. 482, (2018) involved Alcotest calibration records and resulted in the Court holding certain breath-test results inadmissible where the machines were not calibrated using a NIST-traceable thermometer.

Has the New Jersey Supreme Court approved the Alcotest 9510?

The Supreme Court opened a statewide proceeding to consider the scientific reliability of the Alcotest 9510 in State v. Cunningham, but that proceeding was dismissed in December 2025 after the defendant withdrew her challenge. The Court therefore did not issue a merits ruling resolving the 9510’s scientific reliability. It lifted the stay and expressly permitted individual defendants to raise reliability challenges in their own cases.

Can Alcotest calibration records be challenged?

Yes. Calibration records are part of the foundation for breath-test evidence and should be examined for compliance, accuracy, certification, and consistency.

Can I obtain my own independent alcohol test?

New Jersey’s implied-consent statute provides that a person tested by police may have independent chemical testing performed by a person or physician of their own selection.

Is refusing the breath test the same as challenging the breath result?

No. Refusal is a separate offense governed by New Jersey’s implied-consent laws. Challenging a breath result involves attacking the admissibility or reliability of a test that was actually performed.

Challenging Alcotest Evidence in a New Jersey DWI Case

A BAC number can be powerful evidence, but the number is only as reliable as the testing process that produced it.

A proper defense should determine which Alcotest model was used, whether the instrument was properly calibrated, whether the operator was certified, whether the 20-minute observation requirement was satisfied, whether supporting records are complete, whether video confirms the written documentation, and whether any scientific or procedural issue affects admissibility.

Cases such as State v. Chun, 194 N.J. 54, (2008) and State v. Cassidy, 235 N.J. 482, (2018) demonstrate why breath-test evidence requires a proper scientific and procedural foundation. The more recent Alcotest 9510 litigation also makes it important to identify exactly which machine generated the result in a current case.

William Proetta Criminal Law reviews Alcotest records, calibration documentation, police video, operator certification, observation procedures, scientific evidence, and the circumstances surrounding the breath test when defending DWI charges throughout New Jersey.

If you have been charged with DWI, call (201) 793-8018 in Jersey City or (732) 659-9600 in Edison for a confidential consultation.

For a complete overview of New Jersey DWI law and defense issues, visit our New Jersey DWI Lawyer and Defense Guide.