Pennsylvania's BAC tiers
75 Pa.C.S. § 3802 sets out alcohol DUI in tiers:
- General impairment, § 3802(a)(1): drinking enough alcohol to be incapable of driving safely. No specific BAC number is required.
- General impairment, § 3802(a)(2): a BAC of 0.08% to under 0.10% within two hours after driving.
- High rate, § 3802(b): 0.10% to under 0.16% within two hours.
- Highest rate, § 3802(c): 0.16% or higher within two hours.
Lower limits apply to drivers under 21 (0.02%), commercial vehicles (0.04%) and school buses and school vehicles (0.02%). See our under-21 DUI page for the zero-tolerance rules.
The tier matters because penalties, license suspensions and ignition interlock requirements climb with it. Our PA DUI penalties article walks through each tier.
The two-hour rule
For the BAC-based charges, the law looks at your alcohol concentration within two hours after you drove, not hours later at the hospital. If the blood was drawn more than two hours after driving, the result can be used to prove a specific tier only if the Commonwealth shows both of the following, under § 3802(g):
- Good cause explaining why the sample couldn't be obtained within two hours.
- That you didn't drink alcohol or use a controlled substance between the arrest and the blood draw.
The two-hour rule doesn't apply to general impairment under § 3802(a)(1), which doesn't depend on a specific number, and the drug DUI sections don't use a two-hour window. So a late draw doesn't end the case. It can, however, weaken a high or highest tier charge if the Commonwealth can't justify the delay.
Questions worth asking about timing
- What time did you actually stop driving, and who says so?
- When was the blood drawn? Hospital records and the police report don't always match.
- If the draw was late, what is the Commonwealth's reason?
- Did you have anything to drink after you stopped driving but before the arrest?
Calls answered Mon–Fri, 9am–6:30pm; after-hours by appointment
John Gentry, Esq.500+ criminal and DUI cases · Licensed since 2007
How the blood test itself can be challenged
A blood result is only as reliable as the process behind it. Under § 1547(c), a blood test done in Pennsylvania must be performed by a clinical laboratory licensed and approved by the Department of Health, or by a Pennsylvania State Police crime lab, using approved procedures and equipment. Common issues include:
- Chain of custody: who drew the blood, how the tube was sealed and labeled, how it was stored and transported, and whether every hand-off was documented.
- The sample itself: whether the correct collection tubes were used and how the sample was stored before testing.
- Lab procedures: the lab's approval, its testing method, its calibration and quality-control records, and whether the result was confirmed.
- Serum versus whole blood: hospital labs often test serum or plasma, which typically reads higher than whole blood. How a hospital result was converted matters.
- Consent or a warrant: after Birchfield v. North Dakota, police generally need a warrant or valid consent for a blood draw, absent an emergency. See refusing a breath or blood test.
Some arrests use a breath test at the station instead of blood. Under § 1547(c)(1), breath machines must be approved by the Department of Health and calibrated and tested for accuracy on a set schedule, and the operator must be trained on the device. Calibration and accuracy logs are often among the first records to request in a breath case.
You are entitled to the results of any chemical test on request under § 1547(g). Under § 1547(h), you can also have a physician of your choosing do an additional test, although police don't have to delay their own test for it. In some cases, an independent toxicologist reviews the lab file.
Drug DUI under § 3802(d), including THC
Drug DUI works differently. Under § 3802(d)(1), it is illegal to drive with any amount in your blood of a Schedule I controlled substance, a Schedule II or III drug that wasn't prescribed to you, or a metabolite of either. That section doesn't require proof of impairment. Separate sections, § 3802(d)(2) and (d)(3), cover being impaired by drugs, or by drugs and alcohol together.
Marijuana is a Schedule I substance under Pennsylvania law, so THC or a THC metabolite in your blood can support a § 3802(d)(1) charge even if you weren't impaired and used it well before driving. In Commonwealth v. Dabney (2022), the Superior Court held that a medical marijuana card is not a defense to this charge. Bills to change that have been introduced, but as of October 2026 none has become law.
Products sold as hemp, CBD or Delta-8 can still produce a THC result. Whether a particular compound and level fits the statute is a lab question and a legal question, and both are worth checking with care.
Minimum levels and drug test challenges
Under § 1547(c)(4), the Department of Health sets minimum levels of drugs and metabolites that must be present for a blood result to be admissible in a drug DUI prosecution. In drug cases we look at which compounds were reported, whether each was at or above the minimum, whether a prescription covers a Schedule II or III result, and the same chain-of-custody and lab issues as in alcohol cases.
A § 3802(d) charge is sentenced like the highest tier, and it can make a repeat case a felony. See felony DUI in PA, and our drug charges page if you were also charged with possession. Blood results can take several weeks, so charges are often filed by summons after the arrest. That waiting period is a good time to start reviewing the case.
This page is general information, not legal advice.
Prior results do not guarantee a similar outcome. Pennsylvania DUI law changes often, and this page reflects the law as of October 2026. Every case depends on its own facts.