The facts showed that on May 31, 2006, Appellee was charged by criminal complaint with driving under the influence of a drug to a degree which impairs the ability to drive safely, following an incident that took place on May 5, 2006. The criminal complaint was based on an eyewitness's account of the reckless and dangerous manner in which Appellee was driving; on a police officer's observations of Appellee, including her failure to pass three field sobriety tests; and on the detection in Appellee's blood of Diazepam (Valium), at 95 nanograms per milliliter, and Nordiazepam, at 220 nanograms per milliliter, along with Appellee's acknowledgement that she had taken a different prescription medication, specifically, Soma 350, on the morning of the incident. Police also found prescription pill bottles for Soma in the open center console of Appellee's vehicle.
A bench trial was held on March 7, 2007, at which only two individuals testified: the eyewitness who observed Appellee's reckless driving and then called 911, and Officer William H. Dillman, the experienced police officer who responded to the call. In addition, the parties stipulated that both Diazepam and Nordiazepam are Schedule IV controlled substances, and that the amounts found in Appellee's bloodstream were, respectively, just below or in the therapeutic range. The trial court convicted Appellee.
A divided panel of the Superior Court reversed Appellee's conviction. Although no member of the panel disputed the trial court's finding that Appellee was incapable of safely driving on the afternoon of the incident that led to her arrest, the majority held that the evidence was insufficient to sustain Appellee's conviction. Commonwealth v. Griffith, 985 A.2d 230, 235–36 (Pa.Super.2009). Under the majority's reasoning, the laboratory tests revealed only the presence of prescription medications in Appellee's blood, and it was improper for the fact-finder to infer the effect of those prescription medications on the human body in the absence of expert testimony. Id. at 236. The majority contrasted the generally understood intoxicating effect of alcohol with the various effects of prescription medications: the effect of alcohol “is widely known and recognized by the average layperson, [but] the same cannot be said [concerning the effects] of prescription medications.” Id. Accordingly, the panel majority set forth a rule requiring expert testimony as to the effects and interactions of prescription medications when such medications are the alleged intoxicants in a subsection 3802(d)(2) prosecution. Id.
The statute at issue is the following:
(d) Controlled substances.-An individual may not drive, operate or be in actual physical control of the movement of a vehicle under any of following circumstances:
(2) The individual is under the influence of a drug or combination of drugs to a degree which impairs the individual's ability to safely drive, operate or be in actual physical control of the movement of the vehicle.
On appeal from the appellate court's reversal of the conviction, the Supreme Court concluded that expert testimony was not an absolute prerequisite, stating:
"After analyzing the relevant statute in its entirety and in its proper context and considering the Superior Court's analyses discussed above, we decline to read into subsection 3802(d)(2) a mandatory requirement for expert testimony to establish that the defendant's inability to drive safely was caused by ingestion of a drug, even if it is a prescription drug, or drug combination. We do not dispute that in some cases, depending on the specific facts and circumstances, expert testimony may be helpful, or perhaps even necessary, to prove causation under subsection 3802(d)(2), but we decline to hold that the need for expert testimony is inherent in the statutory provision and thus mandatory in all cases."
"Our decision derives, in large part, from a comparison of those provisions of Section 3802 that concern alcohol consumption versus those that concern drug usage. Most of the alcohol-related provisions, i.e., subsections 3802(a)(2), (b), and (c), prohibit driving after an individual has imbibed sufficient alcohol such that the alcohol concentration in that individual's blood or breath reaches certain, specific levels within two hours after driving. To prove the specific level of alcohol in the defendant's blood or breath at the relevant time, a blood or breath test is obviously required. In contrast, under the general impairment provision set forth in subsection 3802(a)(1), a blood or breath test to determine alcohol level is not required; rather, a different standard is used, to wit, “imbibing a sufficient amount of alcohol such that [one] is rendered incapable of safely driving.” We have made clear that Section 3802 neither specifies nor limits the type of evidence that the Commonwealth may proffer to prove its case under subsection 3802(a)(1). Commonwealth v. Segida, 985 A.2d 871, 879 (Pa.2009) (citing Commonwealth v. Kerry, 906 A.2d 1237, 1241 (Pa.Super.2006)). Although the Commonwealth may proffer evidence of alcohol level and/or expert testimony to establish that the defendant had imbibed sufficient alcohol to be rendered incapable of driving safely, it is not required to do so under subsection 3802(a)(1). Id. This is well-established, long-standing law in Pennsylvania. See, e.g., Commonwealth v. Horn, 150 A.2d 872, 875 (Pa.1959) (under a prior version of the statute, making clear that medical opinion is admissible but not required to prove that a defendant operated a motor vehicle while under the influence of intoxicating liquor). As we stated in Segida, supra at 879, “[r]egardless of the type of evidence that the Commonwealth proffers to support its case, the focus of subsection 3802(a)(1) remains on the inability of the individual to drive safely due to consumption of alcohol-not on a particular blood alcohol level.” Thus, as an important practical consequence of this statutory scheme, a drunk driver who declines to submit to a blood or breath test to determine alcohol level can still be charged with and convicted under subsection 3802(a)(1) if the Commonwealth can prove that he or she drove after imbibing a sufficient amount of alcohol such that he or she was rendered incapable of safely driving."
The General Assembly chose to construct a similar statutory framework with regard to prohibitions against driving after drug usage. First, subsection 3802(d)(1) prohibits one from driving if there is any amount of a Schedule I controlled substance, any amount of a Schedule II or Schedule III controlled substance that has not been medically prescribed for the individual, or any amount of a metabolite of a controlled substance in one's blood. Analogously to subsections 3802(a)(2), (b), and (c) for alcohol intoxication, subsection 3802(d)(1) requires a measurement to determine if any amount of a Schedule I, II, or III controlled substance is detectable in the defendant's blood. Second, and analogously to subsection 3802(a)(1) for alcohol intoxication, subsection 3802(d)(2) prohibits driving if one is “under the influence of a drug or combination of drugs to a degree which impairs [one's] ability to safely drive.” This provision by its plain text does not require that a drug be measured in the defendant's blood, nor does it specify any particular manner by which the Commonwealth is required to prove that the defendant was under the influence of a drug. Like subsection 3802(a)(1), see Segida, supra at 879, subsection 3802(d)(2) does not limit, constrain, or specify the type of evidence that the Commonwealth can proffer to prove its case. Given the general nature of subsection 3802(d)(2)'s prohibition, the textual similarity of subsection 3802(d)(2) to subsection 3802(a)(1), and Section 3802's overall structure, we decline to impose a requirement for expert testimony in all prosecutions under subsection 3802(d)(2)."