If you are pulled over by police and asked to submit a test of your blood alcohol concentration, there is a good chance this traffic stop could eventually lead to first offense DUI charges if you are over the limit. You need to be aware that scientific evidence obtained by a BAC test can be used by a prosecutor against you, as long as it was lawfully collected.
However, if your constitutional rights were violated in the collection of evidence, prosecutors may not present it to a jury and the evidence can be suppressed. Furthermore, even if scientific evidence is obtained, you can still sometimes avoid an DUI conviction by making the jury doubt whether or not the testing process was accurate.
Pennsylvania has implied consent laws, which are laws requiring drivers to submit to a BAC test. Section 1547 of the PA code establishes the rule that: "Any person who drives, operates or is in actual physical control of the movement of a vehicle in this Commonwealth shall be deemed to have given consent to one or more chemical tests of breath or blood for the purpose of determining the alcoholic content of blood or the presence of a controlled substance if a police officer has reasonable grounds to believe the person to have been driving, operating or in actual physical control of the movement of a vehicle" while unlawfully intoxicated.
Refusal to submit to a test when there is reasonable cause to believe you are impaired can result in a 12-month license suspension for a first offense and can result in a lengthier suspension if you have a past history of related convictions.
While the consequence of having your license suspended is severe, the state cannot impose criminal penalties for refusal to submit to a blood test. The Washington Post indicates the Supreme Court recently had this type of practice was unconstitutional.
Before the Supreme Court's recent decision, an increasing number of states had begun to make it a crime for a driver to refuse a blood test, even if there was no warrant for the blood test. States did this to essentially force consent. The Supreme Court found that without a warrant, a state could not coerce consent to a blood test. States could, however, require a driver give consent to a breath test, which is not as invasive.
Defendants need to understand the constitutional protections and the protections extended by the court. If your traffic stop or the required BAC test was not constitutional because there were no reasonable grounds for police to either pull you over or to require you to take the test, then any evidence collected cannot be used against you. An attorney can help you to understand the rules and can make a motion to suppress evidence which was obtained by law enforcement in violation of the protections afforded to you.