Testing Methods

Law enforcement officers in the state of Arizona may use three types of tests to investigate whether or not drivers are driving under the influence (DUI). State law allows tests that involve a suspect's blood, breath and urine when trying to determine the presence of alcohol in a driver's system at the time they were suspected of DUI. These tests are referred to as chemical tests because they use chemical means in order to make that determination.

Each of these tests has a specific purpose and each may be challenged. It is not something you should navigate without legal representation like an experienced Arizona DUI lawyer like the Law Offices of Craig W. Penrod, P.C.

Testing a person's breath for the presence and the alcohol concentration has been around for a very long time and is the test of choice for law enforcement officers in the field and do not have access to a laboratory. A breath testing device requires a suspect to blow into a mouthpiece and as a method to determine the alcohol content on the breath of a DUI suspect. This type of breath test is not considered to be as reliable as a blood test. Thus, breath tests are often used to support an arrest and a blood test is conducted at a later time in order to confirm the results of the breath test.

Instruments used to test a suspect's breath rely on a scientific principle known as Henry's Law or Henry's Coefficient, in which English physicist William Henry was able to show that the rate at which molecules traveled into a gas was constant, thus when someone blows into the breath test instrument, the device measures the amount of alcohol present in the breath and converts that measurement into an equivalent blood alcohol concentration (BAC).

Henry's Law also applies to the testing of blood, but this test deals with coefficients present in liquids instead of gases. While blood tests are believed to be more accurate than the testing of breath, as it may be affected by the period of time since a person has ingested alcohol, the size of the person's body and body fat ratio, as well as other factors.

Urine tests are allowed in the state of Arizona, but they are rarely used by law enforcement officers as evidence in support a DUI charge. Urine tests are primarily used as an investigative tool when there is a suspicion that the suspect has been using some type of drugs. A byproduct of many drugs are metabolites, which like most waste products in the bloodstream, are removed through urination. An investigative issue is that it is, generally, impossible to determine from a urine sample when a suspect ingested the drugs.

An attorney may be able to assist suspect's who are fighting DUI charges based upon the limitations of scientific testing. With all of the potential repercussions of a driver's license suspension, plus an arrest and a conviction for DUI, it is vital that your legal situation should be handled by expert professionals with the experience possessed by the attorneys at the Law Offices of Craig W. Penrod, P.C.

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