Blood Alcohol Concentration (BAC) Testing – Payson

Police and prosecutors consider your blood alcohol concentration, or BAC, to be one of the strongest pieces of evidence in a DUI case. Still, several factors can lead to inaccurate BAC testing. Mishandling or contamination of blood samples, malfunctions with BAC testing devices, and user error all could cause erroneous BAC results.

Payson DUI Defense Lawyer

If you are arrested for DUI in Payson, you should immediately request to speak with an attorney before consenting to any BAC test.

Also, if you have already been charged with DUI in Payson and the police took a blood or breath sample from you for BAC or drug toxicology testing, then you will need an attorney that is ready and willing to challenge the reliability of the government’s tests.

Types of BAC Testing

The most common types of BAC testing used in Payson DUI arrests are “Intoxilyzer” (breathalyzer) and headspace gas chromatography testing (blood testing).

Officers take blood or breath samples to determine your BAC. They need to take precautions when administering and analyzing these tests. If police or lab technicians cut corners, then the BAC results could be skewed.

We work with experts in forensic toxicology to stay up to date on the latest issues in the BAC testing, so we can mount aggressive DUI defenses based on cutting-edge scientific data.

Payson BAC Testing Attorney

Portable Breath Test (PBT)

In many DUI cases you complete a breath test close to where the police officer initiated the interaction with you. You’ll use a small handheld device called a Portable Breath Test, or PBT. The PBT takes one breath sample and uses that to give an estimate of your BAC.

Many PBTs rely on fuel cell technology to estimate your BAC, using an electrochemical process to oxidize the alcohol in your breath sample. This produces an electrical current which the PBT uses to calculate your BAC, which is then displayed on a small screen.

Officers use these devices because they are quick and easy, giving them a BAC estimate in a matter of seconds. But quick and easy is rarely a good thing when it comes to the criminal justice system.

Compared to other BAC test methods, PBT devices are rudimentary and often produce inaccurate results. In fact, a BAC determined by a PBT is not admissible in Arizona courts, so it is essentially only used by police officers to make arrest decisions in the field. If you were given a PBT on the side of the road, whatever result it gave will not be admissible against you in a criminal trial.

This begs the question, though, of what happens in the event of a refusal.


The Intoxilyzer is a breath testing device that is much larger than a PBT. It is often kept at the police station or in a dedicated DUI van. You blow two separate times into a flexible tube connected to the device and the machine produces two BAC readings using infrared spectroscopy.

Unlike with a PBT, a BAC determined by an Intoxilyzer is typically admissible in a criminal case.

Challenging BAC Test Results

Calling Intoxilyzer results a “BAC” is a bit of a misnomer, because this machine does not test your blood. An Intoxilyzer is calculating a different kind of BAC, “Breath Alcohol Concentration.”

Although the Intoxilyzer may seem more scientific than a PBT, it is not without its pitfalls. There are several defenses that the DUI attorneys at the Rosenstein Law Group use to challenge a BAC determined by an Intoxilyzer.

We review Intoxilyzer maintenance records to determine whether ere are any known issues with each machine. Each machine goes through periodic checks from a Quality Assurance Specialist (QAS). If the QAS does not complete the required quality assurance checks properly or in a timely manner, we can use this to challenge the results or even to suppress the evidence altogether.

Additionally, the two breath tests must be preceded and followed by proper air blanks and must be within .020 of each other.

The Arizona Department of Public Safety allows for a very high 10 percent range of accuracy for Intoxilyzer machines. An experienced attorney knows that the accuracy of an Intoxilyzer can vary by much more than 10% because of environmental variables.

Among other issues, residual mouth alcohol, your breath temperature, and the way in which you breathe into the machine can all affect the reliability of the results.

Speak With An Aggressive DUI Defense Law Firm Today

Every case has its own unique factors that could affect the reliability of an Intoxilyzer test. Contact the attorneys at the Rosenstein Law Group for a free consultation at 480-248-7666 or online to see what factors may have affected your Intoxilyzer reading.

Blood Testing (Headspace Gas Chromatography)

Blood testing is now a common occurrence in DUI arrests. An officer or other qualified phlebotomist will draw two tubes of blood from an arrestee and submit the blood to a lab for testing.

The testing method used throughout Arizona is headspace gas chromatography. This testing method involves a lab technician pipetting known controls and calibrators into a machine along with blood samples from people that have been arrested for DUI. The controls and calibrators are used to make sure that the machine can detect certain levels of ethanol and accurately determine a BAC.

Effectively Defending Against Inaccurate BAC Evidence

It is important to know that the Intoxilyzer can be very sensitive to human error. Although there may be problems with the machine itself that could cause accuracy issues, the risk of human error during the preparation of the samples, calibrators, or controls is greater. This is because it can be difficult if not impossible to detect the error by looking at the data produced by the machine after a test. This could result in erroneous BAC readings that a prosecutor or lab technician will not hesitate to rely on to prosecute you.

With a smart, comprehensive investigation into all the aspects of your case, including the roadside field sobriety tests, driving behavior, drinking history, blood draw and toxicology testing, one of our experienced DUI defense attorneys can mount an aggressive defense to challenge the prosecutor’s BAC evidence.

Payson DUI Lawyer – Available 24/7

The attorneys at the Rosenstein Law Group have substantial experience dealing with forensic evidence. We also work closely with leading forensic experts to mount unique defenses based on the facts of each case.

A good DUI defense attorney will not only review the scientific testing data to challenge the BAC results but will also use facts gathered from your roadside interaction with the police to attack the credibility of the prosecution’s BAC evidence. This comprehensive approach is necessary to get you the best possible result, which may include suppressed evidence, reduced charges, a dismissal, or complete acquittal.

Contact the Rosenstein Law Group at 480-248-7666 or online for a free consultation and preliminary case evaluation.


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