Three Factors Prosecutors Consider When Establishing a DUI Case

Understanding How the Commonwealth Builds a DUI Case

In Pennsylvania, prosecutors must satisfy several legal requirements before they can secure a DUI conviction. The Commonwealth carries the burden of proving guilt beyond a reasonable doubt, one of the highest standards in the law. At SKA Law Group, Attorneys Michael Kotik and Amato Sanita evaluate every DUI case by examining three core elements prosecutors rely on. When any one of these elements is unsupported, incomplete, or unconstitutional, the defense may be able to suppress critical evidence or defeat the charge entirely.

1. The Legality of the Traffic Stop: Reasonable Suspicion or Probable Cause

A DUI case begins with the traffic stop. For the stop to be lawful, police must have:

• Reasonable suspicion that a traffic violation or criminal activity is occurring, or

• Probable cause for a non-investigatory stop (such as for a traffic offense)

Under Pennsylvania law, an unlawful stop can violate the Fourth Amendment. Courts have held that any evidence obtained after an illegal stop—including field sobriety tests, breath tests, and police observations—must be suppressed.

This principle comes from long-standing case law, including Commonwealth v. Chase and Terry v. Ohio at the federal level.

Examples of stops that may be challenged include:

• No visible traffic violation

• Officer misinterpreting lawful driving behavior as impairment

• Anonymous tips lacking corroboration

• Stops based solely on hunches or assumptions

If the stop is invalid, the prosecution often loses the majority of its evidence, and the case may be dismissed.

2. Proof That the Defendant Was Driving or in “Actual Physical Control”

The Commonwealth must prove the defendant:

• Was driving the vehicle, or

• Was in actual physical control of it (as defined by Pennsylvania DUI statute 75 Pa.C.S. § 3802)

This element can be difficult for prosecutors when:

• The defendant is found outside the car

• The vehicle is parked or stopped with no direct evidence of driving

• Multiple people were present at the scene

• There are no eyewitnesses placing the defendant behind the wheel

Pennsylvania courts have repeatedly dismissed DUI charges when the Commonwealth fails to identify the driver. Cases such as Commonwealth v. Byers illustrate that “mere presence near a vehicle” is not enough to prove actual physical control.

Factors prosecutors may use to argue actual physical control include:

• Keys in the ignition

• Engine warm or recently running

• Defendant seated in the driver’s seat

• Location of the vehicle (e.g., parked in a travel lane)

However, each of these factors can be challenged, and many DUI cases fall apart when the prosecution cannot satisfy this requirement.

3. Probable Cause to Believe the Defendant Was Impaired

After establishing a lawful stop and proving control of the vehicle, the prosecutor must show that police had probable cause to believe the defendant was under the influence.

Probable cause may come from a combination of factors, such as:

• Odor of alcohol or marijuana

• Bloodshot or glassy eyes

• Slurred or slowed speech

• Poor performance on standardized field sobriety tests

• Admissions of drinking or drug use

• Erratic driving behavior

• Portable breath test (PBT) indications

• Blood or breath test results

Pennsylvania follows guidance from the National Highway Traffic Safety Administration (NHTSA) for administering field sobriety tests. However, these tests are not foolproof. Improper instructions, uneven ground, medical conditions, fatigue, and stress can all invalidate their reliability.

Important legal note:

A PBT alone cannot be used as proof of guilt at trial—only to help establish probable cause (75 Pa.C.S. § 1547(k)).

If probable cause is weak or unsupported, the defense can argue that the officer should never have arrested the defendant, leading to suppression of chemical tests and other evidence.

How These Three Elements Shape Your DUI Defense

When all three elements are sound, the Commonwealth often believes it has a strong DUI case. But if any of the following exists:

• An unlawful stop

• Unclear evidence of driving

• Insufficient probable cause

• Faulty sobriety testing

• Improper chemical testing procedure

• Chain-of-custody issues

• Contradictions in officer testimony

…the prosecution’s case may be significantly weakened.

A skilled defense team can file motions to suppress, challenge test results, question officer credibility, and present evidence that undermines the Commonwealth’s theory. In many cases handled by SKA Law Group, these challenges result in reduced penalties, charge withdrawals, or full dismissals.

Contact SKA Law Group for a Comprehensive DUI Case Review

If you want to understand how your charges fit within these legal elements, contact SKA Law Group at 267-265-4553. Attorneys Michael Kotik and Amato Sanita will carefully analyze your traffic stop, the evidence against you, and the strength of the prosecution’s case. Our team will develop the strongest defense strategy to protect your rights, your license, and your future.