The Role of Chemical Tests in DUI Cases

In Arizona, chemical tests are almost always used as part of a driving under the influence (DUI) criminal investigation. These tests measure the amount of alcohol or drugs in a person’s body at the time of a DUI arrest. Chemical tests may rely on the individual’s breath, blood or urine. If the test results show that someone is under the influence of drugs and/or alcohol, it can be used as evidence in a DUI case.

Arizona’s Legal Limit

In Arizona, it is against the law to drive or be in actual physical control of a vehicle while under the influence of an intoxicating liquor, any drug, a vapor-releasing substance containing a toxic substance, or any combination thereof if the individual is impaired to the slightest degree (Arizona Revised Statutes Section 28-1381). This is the crime known as driving under the influence, which can result in penalties such as a fine, driver’s license suspension and jail time.

The law also states that if a person has a blood alcohol concentration (BAC) level at or above 0.08 within two hours of driving or being in actual physical control of a vehicle, he or she is presumed to be intoxicated. If the individual is operating a commercial motor vehicle, however, the legal BAC limit is 0.04 percent. Under Arizona’s Zero Tolerance law, a driver under the legal drinking age of 21 can be arrested for a DUI with any discernible amount of alcohol in his or her system.

The Use of Chemical Tests During a DUI Case

Chemical tests can provide evidence for the prosecution against someone being accused of driving under the influence. The results of the chemical tests performed at the time of the arrest or shortly after could be used to establish that alcohol or a controlled substance was in a driver’s system within two hours of driving. 

Every driver in Arizona gives his or her implied consent to take a breathalyzer test. If this test is refused, the driver’s license will be suspended for a year. If a chemical test shows that the driver was at or above the legal BAC limit, the test results will provide central evidence to a DUI per se case. DUI per se means that a driver can be found guilty of DUI based on an illegal BAC level alone, even if it is not proven that he or she was actually under the influence. 

Even if a chemical test shows a BAC that is lower than the legal limit, however, the driver could still be convicted of driving under the influence. It is illegal to operate or be in actual physical control of a vehicle while “impaired to the slightest degree.” The prosecution could argue that a driver was impaired based on any amount of a substance confirmed by a chemical test.

Can You Argue Against Chemical Test Evidence?

Yes. If you are accused of driving under the influence, a DUI defense lawyer in Scottsdale will examine your case to determine the best possible defense for your situation. Your lawyer will search for holes in the prosecutor’s case against you. This may include arguing against chemical test evidence obtained during a DUI arrest. It may be possible to use the following defenses:

  • Unreliable test results
  • Inaccurate breathalyzer test
  • The equipment was not correctly calibrated
  • Poor equipment maintenance
  • Poorly trained officers or staff
  • Inaccurate suspect observation times
  • Unacceptable testing or medical practices
  • Contamination of evidence
  • Missing test results

Chemical tests are subject to many variables that can affect their accuracy. Your lawyer can argue against the reliability of the test results to aid in your defense. It may also be possible to argue that you were not impaired despite the results of a urine, blood or breath test. An experienced DUI lawyer can explore all possible defense strategies and may push to have chemical test evidence dismissed or ruled as inadmissible. 

Even if chemical test results show a high BAC level, this does not guarantee a conviction. If you’ve been arrested for an alleged DUI, contact a Scottsdale DUI defense attorney for assistance.

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