Published on:

Anatomy of a Pennsylvania DUI Offense: How is “Impairment” Defined?

Driving while under the influence of drugs or alcohol, commonly known as “driving under the influence” or just “DUI,” is a serious offense under Pennsylvania law. Penalties can range from a loss of driving privileges to a lengthy prison sentence, depending on the circumstances. The law in Pennsylvania clearly defines the obligations of police and prosecutors in any case of alleged DUI, and it is critically important for anyone accused of DUI to know their rights. Among the many elements of the offense of DUI that the state must prove, it must provide proof beyond a reasonable doubt that the defendant was impaired by alcohol or illegal drugs.

What is “Impairment”?

Pennsylvania law defines “impairment” very broadly as a state in which a driver is “incapable of safely driving, operating or being in actual physical control of the movement of the vehicle.” Police and prosecutors can gather evidence of impairment by testing a person’s blood or breath, or by observing a person’s behavior and testifying about it in court.

Blood alcohol content (BAC), the percentage of alcohol in a person’s bloodstream at a particular time, is considered by the legal system to be a reliable means of determining impairment. Pennsylvania law presumes that a person is impaired if their BAC is 0.08 percent or higher within two hours of driving. For anyone under the age of 21, or anyone driving a school bus, that amount is 0.02 percent. Commercial vehicle drivers are presumed to be impaired with a BAC of 0.04 percent.

During a traffic stop, a person is generally not obligated to voluntarily cooperate with any sort of warrantless sobriety testing. Refusing to participate may not prevent an arrest, but it also means that the person is not willingly giving evidence to the police to help them make a case for DUI.

How Do Police Determine Impairment?

An officer may ask a driver to perform a field sobriety test, which allows an officer to assess a person’s balance and coordination. This sort of test is based on the theory that an intoxicated person will respond differently than someone who is not impaired by alcohol or drugs, and that these differences are about the same for everybody. Other factors, such as injuries, fatigue, or medical conditions affecting a person’s balance, are rarely taken into account by an officer conducting a field sobriety test.

Police may also ask a driver to submit to a breathalyzer test, which analyzes the alcohol content of a person’s breath, and uses that data to estimate the person’s BAC. Breathalyzer machines can give inaccurate and even false-positive results if they are not properly calibrated or maintained, or if they are not used correctly.

A blood test can also reveal BAC, although these tests may also be prone to error if a sample is collected or handled improperly. Only legally-qualified personnel may draw blood from a DUI suspect. Police usually must have a warrant if the driver does not consent to a blood draw.

If you have been arrested for DUI in Pennsylvania , it is critical that you consult with a qualified DUI lawyer to determine the best way to handle your defense. Zachary B. Cooper, Attorney at Law, P.C. has dedicated 100% of his practice to DUI defense. We are available to help you 24/7. Please contact us online or at (215) 542-0800 for a free and confidential consultation.