Breathalyzer and Blood Tests: Accuracy & Reliability Issues

Portable breathalyzers often play critical roles during field sobriety tests. If a police officer suspects you of driving while under the influence of alcohol, they may require you to blow into a breathalyzer. The device should give the officer your blood alcohol concentration (BAC).

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Depending on the field sobriety test results, which typically include other tests, the officer may arrest and detain you. At the station, they may require you to take another breathalyzer test using a more sophisticated machine than a portable model. Another option for checking your BAC is to draw blood.

DUI - Breathalyzers

Breathalyzer results can influence your chances of getting a DUI conviction. However, it’s essential to understand that breathalyzers may deliver inaccurate results. At De Castroverde Law Group Criminal & Immigration Lawyers, this is one fact we might reference when handling a case like yours. Contact us today to learn more about what our DUI defense lawyers in Las Vegas, Nevada, can do for you.

How Does a Breathalyzer Work?

Not all breathalyzer models are the same. In fact, “breathalyzer” is the name of a popular model of this type of device. We informally use that word to refer to all models of portable breath-testing devices police may use during field sobriety tests.

Because there are different types of breathalyzers, the specific ways they work may vary somewhat from one model to another. Generally, though, checking the alcohol content of someone’s blood with a breathalyzer involves these steps:

  • A subject exhales for a few seconds into a portable mouthpiece. They blow into a chamber that contains a solution of potassium dichromate. In its original state, the solution’s color is orange.
  • Alcohol reacts with the potassium dichromate solution. The solution’s color will change to green in reaction to the alcohol. The more alcohol in a subject’s breath, the more significant the color change.
  • A photocell compares the color of the changed solution to a reference sample in a separate chamber where the solution hasn’t reacted to anything. The difference between the two colors is represented as an electric current. The current triggers the breathalyzer to display a subject’s BAC.

Proper administration is crucial to a breathalyzer’s accuracy. Errors in the process can affect a breathalyzer test’s results.

How Long Can a Breathalyzer Detect Alcohol?

Most breathalyzers can theoretically detect alcohol in a subject’s system up to 24 hours after they consumed it. However, the time a breathalyzer can detect alcohol in someone’s system can depend on the model. Other factors, like how much alcohol a subject consumes, can also influence whether a breathalyzer will still be able to measure their BAC accurately.

Why Breathalyzers May Not Be as Accurate as You Think

Errors during administering a breath test aren’t the only potential causes of inaccurate breathalyzer readings. Consider the following points:

  • Breathalyzers need to be calibrated according to strict schedules. A breathalyzer’s results may be off if it is not appropriately calibrated. According to one report, improper calibration can result in a breathalyzer showing a BAC up to 40 percent higher than a subject’s actual BAC.
  • How deep or shallow a subject’s breaths are can affect a reading. Because a breathalyzer can deliver different results for the same subject, its accuracy may be questioned.
  • Some types of foods and other substances can affect a breathalyzer’s results. For example, a breathalyzer may indicate a subject has a higher BAC than they do if they used mouthwash shortly before taking a breathalyzer test.
  • Medical conditions, such as gastroesophageal reflux disease (GERD), can influence a breath test’s results.

None of this is meant to suggest that you should refuse to take a breathalyzer test when the police ask you to. In Nevada, when you drive, you give “implied consent” to taking a breathalyzer test when law enforcement requests you to do so. If you refuse, your driving privileges will be revoked. The revocation is for a year for the first offense and three years for a second within seven years. 

Challenging Breathalyzer Results in a DUI Case

A criminal defense attorney might challenge the results of a breathalyzer test when defending a client charged with a DUI in various ways. Potential strategies include:

  • Requesting equipment and calibration records An attorney can request the maintenance and calibration records for the breathalyzer the police used during a client’s BAC test. Upon reviewing the documents, they may discover a device wasn’t correctly calibrated. 
  • Challenging the tester’s experience A breathalyzer may deliver inaccurate results if the individual testing a subject makes any mistakes. Thus, an attorney may review the expertise or methods of the tester to determine whether errors during testing contributed to false breathalyzer test results.
  • The timing of the test A person’s BAC doesn’t necessarily reach its maximum level immediately after they consume alcohol. Their BAC can rise over time after they’ve been drinking. Because of this, the timing of breathalyzer tests is crucial. It’s possible that a driver was below the legal limit when they were operating their vehicle. However, by the time they took a breathalyzer test at the station, their BAC may have risen above the legal limit.
  • Arguing that other conditions affected the results Medical conditions, temperature, proximity to certain substances, and other factors may affect a breathalyzer’s results. An attorney can review all the significant details to determine whether any may help them show why breathalyzer results shouldn’t be admissible in your case.

A lawyer can also reference other relevant issues. For example, without even challenging a breathalyzer’s results, an attorney may find evidence to prove that the police didn’t have probable cause to stop their client.

Contact a Las Vegas DUI Defense Lawyer

Challenging the results of a breathalyzer test is just one of many ways we at De Castroverde Law Group Criminal & Immigration Lawyers can work to protect your rights if you’ve been accused of a DUI. A Las Vegas, NV, DUI defense lawyer with our firm can explore all potential options to ensure you receive the defense you deserve. Learn more about how we can help by contacting us online today for a case review.