DUI Chemical Tests And The Law

Three types of DUI Chemical Tests are used to attempt to measure a person’s Blood Alcohol Content (B.A.C.). They are breath tests, blood tests, and the more uncommonly used urine tests. Depending on the circumstances of your particular case and the state you are located in, the police may or may not have discretion as to which test they can request you to submit to. Below, you will find a brief overview of the three different types of chemical tests, and the common problems associated with each. Be sure to check your local laws, however, as this is one area of DUI that greatly varies state to state. Consult with an attorney in your state for more information.

Urine Tests

As mentioned above, Urine tests are the least common of the three DUI Chemical Tests. Urine is only usually requested when police suspect impairment by drugs. These tests are said to be the most unreliable, because of problems that occur with collection of samples and the testing procedures. Urine cannot accurately measure a person’s BAC as well as a blood test can, and usually will only be reliable when detecting levels of narcotics or other illegal substances.

Blood Tests

Blood tests are the most invasive, but also the most reliable – if administered properly they can measure the amount of alcohol present in your blood (BAC). Blood tests are the most constitutionally debated type of test, and some states do not allow the police to draw your blood unless you consent or have been involved in a severe DUI or accident case. Other states, however, do allow the police to obtain a blood sample in any DUI case, regardless of its severity, so long as they have probable cause.

Blood tests can be complex and hard to attack, so if you have submitted to such a test you should consult with an experienced DUI attorney who has a history of fighting blood tests. In some states, your results may be used against you in court unless you can successfully negate its admissibility. Problems with the collection of the sample, the chain of custody, or how the blood was stored until testing are the most common ways to argue against the sample’s scientific validity.

Breath Tests

Breath tests are the most common DUI chemical tests, but also the most problematic. They cannot directly measure the amount of alcohol in your blood. Instead, they try to measure the amount of alcohol on your breath, the results of which are then used to estimate the amount of alcohol that might be in your blood. Most problems with breath tests are a result of improper sample collection, the occurrence of human error, and invalid results obtained on broken machines. Additional factors that may affect your breath test (resulting in an unreliable and false reading) include regurgitation, radio frequency interference, mouth alcohol, and acetone.

So why do so many people take DUI breath test?

Most people facing the choice of taking a DUI breathalyzer test are trying to cooperate with the police. They unknowingly trust that the machine will “prove their innocence.”

Others are worried about what the police tell them about their driver’s license being suspended for refusal.

Are you allowed to consult with a DUI lawyer before you decide to take the test? You may or may not have the right to consult with an attorney before making the decision whether to submit to the test or refuse. In some states, the best thing to do may be to say “Officer, may I speak with an attorney,” and see what he or she says. Always check the individual laws in your state and act only upon the advice of a lawyer whom you have hired who is licensed to practice in the jurisdiction where your DUI is pending.

The Types of DUI Breathalyzer Tests

There are two types of breath tests that exist, and depending on which state you are located, you may or may not be exposed to both. They are Preliminary Breath Tests, which are administered using a handheld breath testing device, and Evidentiary Breath Tests, the more common type of test and the one more likely to be admissible against you in DUI court.

Preliminary Breath Testing:

The preliminary breath test (PBT) is a handheld model used in the field (as distinguished from the larger evidentiary breath test models such as the Intoxilyzers covered below). They typically have an LCD readout, and lack the ability print the result.

In most states the PBT is generally not admissible into evidence in court. This means that the prosecutor and police can not use the results against a person accused of DUI in trial. Furthermore, in the states that prohibit its admissibility, a suspect usually has an absolute ability to refuse to submit to this test and it can not legally be held against them.

Why is the preliminary breath test used in DUI investigations? The preliminary (sometimes referred to as the portable breath test) is a tool used by law enforcement to establish probable cause to arrest a person, and also to give the officer a ballpark estimate of what an evidentiary breath test or blood test might produce. If you pass all of the field “sobriety” tests and blow above or close to the legal limit on the PBT, the officer will likely arrest you despite your good performance on the field tests. The officer can then rely on the results of this test to convince a Judge in your DUI or administrative review hearing that your arrest was legal.

Another recent use for the PBT has been in impounding vehicles. Some jurisdictions have DUI impound laws where the police in extreme cases will take almost exclusively blood tests, but can detain vehicles of suspects over a certain BAC amount. An officer can justify impounding your vehicle if he has obtained a reading of your BAC level on the scene. On the other hand, if you politely refuse to take this test then there may not be not enough evidence to sustain a decision to impound.

What if I know I’m below the legal limit… should I blow into the PBT?

This is a question that should be addressed to a local attorney, because the advice may vary from state to state. As a starting point, however, these machines are inaccurate. If blow it could make the difference between you being arrested or not. On the other hand, the officer will probably arrest you if you refuse. Nevertheless, some DUI lawyers think the better course of action is to politely refuse and let a blood test (or evidentiary breath test) sort it out (see below discussion of the right to an independent test).

PBTs are good party entertainment, and they are very useful in determining if there is alcohol in a persons system. However, they are not good at predicting a specific alcohol level, and they are not designed to detect impairment.

The most common PBTs are the Intoxilyzer 300 and the Alco-Sensor.

Evidentiary Breath Testing:

There are several brands of evidentiary breath tests available on the market. The leading manufacturers are:

• CMI – A company out of Kentucky that makes the Intoxilyzer line of breath test devices. The current device is the Intoxilyzer 8000. The next older model is the Intoxilyzer 5000, which is still used in many jurisdictions.
• National Patent Analytical Systems – Makers of the DataMaster line of breath test machines. These machines are not as widely used as CMI’s machines, but have gained traction in several states, including Washington State.
• Drager – Makers of perhaps the best and most scientifically defensible breath testing machine.

Currently most jurisdictions use the Intoxilizers. However, the Intoxilyzer line, and CMI in general is currently under heavy fire and criticism from the DUI defense community based on their refusal to disclose the source code that powers the machine. For this reason, many jurisdictions are currently making other plans which include switching to another type of machine or going to an all blood standard.

Every state that uses evidentiary breath testing has a set of regulations in place which dictate how an officer should run the test, how the machine should be maintained, what quality assurance safeguards must be in place, and how the test result gets used in court.

Since each state is different, check the DUI law for the state where you were arrested for specifics of how breathalyzer tests are used.

To find out which test methods and machines are used in your state, select the state of your arrest from the menu below.