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Tolleson DUI Breath Test Lawyer

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Tolleson DUI Breath Test Attorney

There are a couple different kinds of breath testing machines which law enforcement might use after a suspected DUI. The one that often is done on the scene, which is called a portable breath test or preliminary breath test (PBT), is much less accurate and reliable, so much so that it cannot even be used in court. It can be the basis for a probable cause arrest, but it cannot be used in trial to prove guilt beyond a reasonable doubt to a jury.

Even if police give the preliminary or portable breath test on the scene, they will need to do a second test, which is either an intoxilyzer or some other breathalyzer, which is a more scientifically accepted machine that has multiple breath tests. However, there are still issues with those tests that our DUI defense attorneys, like Ryan McPhie, can attack.

Generally, when police take a breath result from someone they think was driving drunk, there is no way to double check if the reading was accurate unless they also do a blood draw to compare. Most will not do this, meaning all they have is the breath result. This opens the door for the Grand Canyon Law Group team to question the role of breathalyzers in Tolleson. Call us NOW to learn your options.


There is a difference between a portable breath test or a preliminary breath test conducted on the scene, and the breathalyzer or intoxilyzer that gets used in police stations. Some people think they can refuse to take one without consequences. In fact, they can refuse one on the scene, but they cannot refuse the one given at the station, without consequence.

Some people think if they refuse, then there is no way that the police can get their blood result, which is not true. If they refuse, law enforcement will get a warrant to get a blood test. If they refuse to allow police to take their blood, they have the right to physically strap the suspect down and take their blood. It does not benefit anyone to refuse.

It is a common misconception among drivers in Tolleson and elsewhere that breathalyzers and intoxilyzers are wildly inaccurate. In fact, there is really no way to know how reliable they are in any given instance, and they can be very convincing to the jury.


It is certainly possible for a breathalyzer to give an inaccurate or false positive BAC reading. It can be something as simple as the person’s body temperature that leads to an inaccurate reading. It can also be different if they burp or regurgitate, have GERD, have a lung ratio different from the average person, or they give too much or too little breath.


Breathalyzers need to be calibrated every 30 and 90 days to test different aspects of it. A prosecutor may argue that a specific device was properly calibrated every time it is used and should be considered accurate. The truth is, sometimes they mess up the calibration tests and the machines do not work properly.

Most law firms do not do this, but at Grand Canyon Law Group, we will ask and require the state to provide us the breathalyzer data from the month prior, and the month after our client had their test done. We will also get the machine’s entire repair history, look for issues where it might not have been fixed correctly or had issues. We also look at the air blanks that are being used to see if that might be inaccurate. Sometimes the 30-day and 90-days tests are not perfectly done and we can challenge the reliability.

Breathalyzers are a lot less expensive, and faster, than running blood samples. That is exactly our argument to a jury – it is less reliable and is not the scientific preference for determining intoxication, yet police and prosecutors use it to decide whether somebody is guilty of a crime so that they can save time and money. Juries generally understand that argument and agree that we should use the best possible method.


Our Tolleson lawyers cannot challenge the breathalyzer and show that the reading was erroneous or wrong. We cannot say, “You got this result, but my client went five minutes later and got their breath analyzed somewhere else and it was different.” We cannot have an independent test unless the driver gets it done later that day, but even then, that will be a different result because their alcohol concentration goes down quickly and the reading is no longer useful.

Our job is to show the breathalyzer is not a reliable machine. We cannot show that this particular reading was erroneous, because we do not have control of the arrest process. It is the police’s duty to show it was correct and we must show there is reason to doubt it.


Some people think their breathalyzer was 0.09, so they will just plead guilty. There is enough wiggle room in breath results to negotiate or potentially take a case to trial because there are real arguments to be made against them. Our excellent attorneys know what to do, so you should call us immediately after you are arrested.

When you are facing a DUI charge after taking a breathalyzer test in Tolleson, call the Grand Canyon Law Group and learn how we might be able to challenge it.

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