PA Court Interprets “Two Hour Rule” for Blood Test Admissiblity in DUI Cases
Posted in DUI on July 8, 2025
In a recent decision that impacts DUI prosecutions across Pennsylvania, the Pennsylvania Supreme Court issued important guidance on how the Commonwealth can prove a “highest rate of alcohol” DUI offense when the exact time of driving is uncertain. The case, Commonwealth v. Starry, 19 WAP 2019, addressed how blood alcohol content (BAC) test results obtained outside the typical two-hour window can still support DUI charges under certain circumstances.
Background: The DUI Highest Rate of Alcohol Offense
Under 75 Pa.C.S. § 3802(c), a person commits a DUI “highest rate” offense if they operate a vehicle with a BAC of 0.16% or higher within two hours after driving. This two-hour requirement exists because of the practical difficulties of measuring someone’s BAC at the exact time of driving, especially in cases involving accidents or medical emergencies.
Section § 3802(g) provides for exceptions to the two-hour rule and allows the Commonwealth to present alcohol testing evidence:
(1) where the Commonwealth shows good cause explaining why the chemical test sample could not be obtained within two hours; and
(2) where the Commonwealth establishes that the individual did not imbibe any alcohol or utilize a controlled substance between the time the individual was arrested and the time the sample was obtained.
The Starry Case: A Question of Timing
In Starry, the defendant was involved in a single-vehicle crash on a rural road in Westmoreland County. When police arrived, they found her slurring her speech, incoherent, and smelling of alcohol. Medical personnel reported finding her asleep in the vehicle. She was transported to the hospital, where a blood test at 1:40 p.m. revealed a staggering BAC of 0.304%—nearly double the threshold for the “highest rate” DUI offense.
The legal issue arose because the exact time of the accident—and therefore the time of her last operation of the vehicle—was uncertain. Phone records showed the accident was first reported at 11:49 a.m., but the defendant had left a nearby residence at approximately 11:00 a.m., creating a potential window of uncertainty exceeding two hours before the blood draw.
Trial Court Dismisses the Charge
The trial court dismissed the highest rate DUI charge at the Preliminary Hearing phase of the case, meaning the judge did not believe that the prosesecution had presented prima facie evidence to support the DUI charge. This was NOT a trial case, meaning one in which the prosecution needed to present proof of guilty beyond a reasonable doubt.
The judge’s ruling was based upon the proseuction’s inability to prove when the defendant last drove, so the prosecution could not prove that the driver’s blood had been obtained within two hours of driving. The court also rejected the application of the statutory exception in 75 Pa.C.S. § 3802(g), which allows for test results beyond two hours if the Commonwealth shows good cause for the delay and no alcohol was consumed after the arrest but before testing.
Superior Court and Supreme Court Reverse
The Pennsylvania Supreme Court disagreed with the ruling and reversed the trial judge’s dimissal. The high court explained that:
The Commonwealth is not strictly required to prove the BAC test occurred within two hours of driving if circumstantial evidence and common sense support the conclusion that the defendant’s BAC exceeded 0.16% within that timeframe.
- In the context of relation back (or extrapolating) from the time of testing to the time of driving, the established a dichotomy between weak and strong inferences
- With regard to weak inferences, these ensue when a defendant’s blood alcohol content is not significantly over the threshold for illegality and/or a substantial period has elapsed between testing and the time of driving, and expert testimony is generally required to support weak inferences.
- A strong inference of guilt can be drawn where there is a substantially elevated test result and the sample was taken relatively close to the time of driving, and expert testimony is not necessary to support strong inferences.
Particularly where there is evidence of an extraordinarily elevated blood test result and the time between the expiration of the two-hour window and testing is reasonably close, the Commonwealth may proceed to a jury determination without the necessity to adduce expert testimony
In this case, the “enormously elevated” BAC of 0.304%, combined with the proximity of the accident report to the blood draw, allowed for a strong inference that the defendant’s BAC was above the legal limit within two hours of driving.
The statutory exception under § 3802(g) offers an alternative way to prove the offense, but it does not preclude the Commonwealth from relying on relation-back evidence to establish the offense under § 3802(c) in the first place.
What This Means for DUI Defense in Pennsylvania
This decision underscores several key takeaways for DUI defense attorneys:
Circumstantial Evidence is Powerful: The prosecution can rely on timing estimates, witness statements, and extraordinarily high BAC results to establish DUI charges, even when the two-hour window is unclear.
Relation-Back Theories Are Permitted: Courts allow juries to infer that a high BAC result reflects the defendant’s condition within the legal timeframe, even without expert testimony, when the BAC is significantly elevated.
The Two-Hour Rule is Flexible: While the statute contains a clear two-hour requirement, courts recognize practical realities in accident and medical situations, giving the Commonwealth flexibility in proving DUI charges.
Defense Strategies Still Exist: Despite this flexibility, defense attorneys can still challenge the timing of events, the reliability of BAC tests, and whether the prosecution’s inferences are reasonable under the specific facts of a case.
Conclusion
The Commonwealth v. Starry decision reinforces the importance of closely analyzing the timing, BAC levels, and available evidence in any DUI prosecution. If you’ve been charged with a DUI, especially one involving a high BAC or accident, an experienced DUI defense attorney can evaluate whether the Commonwealth’s case meets the required legal standards.
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