PA Court Rules on BAC Evidence and the Two-Hour Rule in DUI Cases

Posted in DUI on June 24, 2026

Can the Commonwealth prove a DUI charge even when the exact time of driving is unknown?

In a significant Pennsylvania DUI decision, the Pennsylvania Supreme Court addressed this question in Commonwealth v. Starry, 243 A.3d 364 (Pa. 2020). The case provides important guidance on how prosecutors may prove a DUI charge involving a blood alcohol concentration (BAC) of 0.16% or higher, even when a blood test occurs more than two hours after driving.

The Facts of the Case

Starry was involved in a single-vehicle crash. Witnesses reported the accident at approximately 11:49 a.m., and police arrived shortly thereafter. A state trooper responded to the scene and observed signs of severe intoxication, including: the odor of alcohol, slurred speech, incoherent behavior, and a partially consumed beer inside the vehicle. Starry was transported to a hospital, where a blood sample was drawn at 1:40 p.m. The blood test revealed a BAC of 0.304%, nearly four times Pennsylvania’s legal limit of 0.08%.

The problem for prosecutors was timing. The Commonwealth could not establish the exact moment the defendant last drove the vehicle. Because Pennsylvania’s Highest Rate DUI law under 75 Pa.C.S. § 3802(c) requires proof that the driver’s BAC was 0.16% or greater within two hours of driving, the defense argued that the charge should be dismissed.

The defense argued that not knowing the precise time of driving prevented prosecutors from proving that the blood was drawn within two hours of driving. The trial court agreed and dismissed the Highest Rate DUI charge.

The Pennsylvania Supreme Court’s Decision

The Pennsylvania Supreme Court disagreed with the DUI defense attorney. The Court held that prosecutors may rely on circumstantial evidence and reasonable inferences to prove that a defendant’s BAC exceeded the legal threshold within the required two-hour window. The Court emphasized that a blood test result can be used as evidence of what a person’s BAC likely was at an earlier point in time.

In this case, the defendant’s BAC was 0.304%, an extraordinarily high reading. The Court concluded that a jury could reasonably infer that the defendant’s BAC exceeded 0.16% within two hours of driving, even if the exact time of driving could not be pinpointed.

Strong vs. Weak BAC Inferences

The Court discussed a distinction that often appears in Pennsylvania DUI cases:

Strong Inferences

A strong inference exists when:

In these situations, expert testimony may not be necessary.

Weak Inferences

A weak inference exists when:

Because the defendant’s BAC was 0.304%, the Court found that a strong inference existed.

Why This Decision Matters

The Starry decision is important because it gives prosecutors greater flexibility in proving Highest Rate DUI cases. The Commonwealth does not always need to establish the exact time of driving. Instead, juries may consider:

At the same time, the decision does not eliminate defenses. Every case depends on its specific facts. When BAC levels are lower, testing is delayed, or the timeline is uncertain, there may still be significant challenges to the Commonwealth’s evidence.

DUI Defense in Pennsylvania

A DUI arrest does not automatically mean the Commonwealth can prove its case beyond a reasonable doubt. An experienced Pennsylvania DUI defense attorney can evaluate whether the Commonwealth has sufficient evidence and identify potential defenses available under Pennsylvania law.