Arizona Lawyers discusses whether or not you claim inaccuracy of a BAC test as a defense to a DWI charge.

Can You Claim the Inaccuracy of a BAC Test as a Defense to DWI?

There is not a lot of tangible evidence to be presented when it comes to proving a charge of driving while intoxicated (DWI) in Arizona. The result of most of these cases usually rests on a blood test, which can determine an individual’s blood alcohol concentration (BAC). It is currently one of the most adequate measurements that exist.

In the state of Arizona, someone can be charged with a DWI if their blood alcohol content tests at 0.08 or higher. There are different levels of DWI, such as 0.15 or greater for an Arizona extreme DWI, or 0.20 for an Arizona super extreme DWI. Due to the significance of BAC tests as evidence in a DWI trial, the defendant will often attempt to invalidate the results. 

Despite the fact that these tests are generally looked at as an authority, they are not without risk of error.  Things such as gender, size, and medication are also relevant to the results. Blood or urine tests generally take anywhere from one to six weeks for results. 

How Can You Invalidate a BAC Test?

A BAC test can be invalidated in many ways, including the following:

1. Collecting Blood Improperly

Technicians are responsible for prepping the site and drawing the blood but commonly receive only minimal training. Because of this, they may make a serious mistake that can have a serious effect. Something as simple as taking too big or too small of a sample can result in an error. If the tech fails to properly clean the site of injection or does not prep the area with alcohol swabs, an error can also occur.

2. Failure to Prove Chain of Custody

A chain of custody must be established at all times in a criminal trial for physical evidence. The prosecution has the burden of proving the chain of custody. For instance, a blood sample’s whereabouts must be known at all times from the time that it is drawn. Whenever physical evidence changes hands, it must be recorded in great detail, including the time and date of the transfer.  

3. Incorrectly Storing the Sample

How blood samples are stored can have an effect on the results. Blood samples are to be kept in vacuum-sealed tubes that contain specific chemicals in order to prevent any contamination and to preserve the authenticity of each sample.  Errors such as using expired tubes can impact results. 

4. Testing Samples at the Hospital

While BAC can be tested in a few different ways. When an individual is involved in an accident, he or she often has his or her BAC tested at a hospital. And while this may sound like a secure solution, the results of these tests can be challenged due to how they differ from forensic labs. While forensic labs often test the whole sample, hospitals commonly test only blood plasma, which is more concentrated. Furthermore, certain serious injuries can cause a build-up of lactic acid. Unfortunately, hospital tests are generally unable to differentiate lactic acid from ethyl alcohol. 

5. Incorrect Calibration

In order for blood-testing machines to work properly, they must always be calibrated, similar to Breathalyzers. Machines that are improperly calibrated can lead to an erroneous result and may be excluded. 

Arizona Lawyers Helps Those in Phoenix Who Have Been Charged with a DWI

Much of the outcome of your case is dependent upon BAC test results. Proving these to be invalid can be the difference between a conviction, which will have a serious impact on many aspects of your life or an acquittal. The experienced Arizona Criminal Attorneys at Arizona Lawyers will fight to get you the results you deserve. To learn more or to schedule a free consultation, call us at 602-833-2513 today!

Posted in DWI