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Pennsylvania Field Sobriety Testing

Pennsylvania police officers must undergo specialized training in order to safely and accurately perform a variety of roadside sobriety tests established by the NHTSA. The results of field sobriety tests may be deemed inadmissible in court if a police officer in the state of Pennsylvania was not properly trained to perform such tests.

An experienced and diligent Pennsylvania DUI attorney may be able to successfully challenge any field sobriety test results. Furthermore, if field sobriety tests are used as a basis for conducting a breath or blood test, the results of the blood or breath tests may be inadmissible at trial. Our skilled and determined DUI defense lawyers have extensive experience representing clients in DUI cases in Delaware County, Philadelphia County, Chester County, Bucks County, Northampton County, and the greater tri-state area.

Below, you will find the field sobriety tests currently being conducted by properly trained Pennsylvania law enforcement officers. If you were recently asked to perform any field sobriety test not mentioned below, the results of the test cannot be used against you in a court of law.

Standardized Field Sobriety Test

Commonly known as the SFST, the Standardized Field Sobriety Test actually consists of three tests that must be conducted in a standardized manner in order to reveal validated impairment indicators and establish the probable cause needed for an arrest. The three tests that make up the SFST were developed thanks to research from the Southern California Research Institute and sponsorship from the National Highway Traffic Safety Administration.

The NHTSA developed a formal training program for police officers administering the SFST in an effort to help them better detect DUI suspects, accurately describe their behavior, and effectively testify in court. The program is administered and accredited by the International Association of Chiefs of Police. The three SFST tests include:

  • Horizontal Gaze Nystagmus Test
  • Walk and Turn Test
  • One-Leg Stand Test

These three tests are systematically administered and evaluated based on the measured responses of a suspect.

Horizontal Gaze Nystagmus Test

The Horizontal Gaze Nystagmus test, or HGN test, determines if a person is impaired by having him or her track an object as it moves from side to side. HGN is an involuntary eye jerk that naturally occurs when a person’s eyes gaze from side to side. When a person is not impaired, nystagmus takes place when their eyes rotate at high angles. When a person is impaired, however, their nystagmus is exaggerated and takes place at lesser angles. A person impaired by alcohol will also find it difficult to smoothly follow a moving object.

When performing an HGN test, an officer observes a suspect’s eyes as they horizontally follow a small flashlight, pen, or other moving object. The officer then looks in each eye to observe any of the following three signs of impairment:

  • Inability to smoothly follow a moving object
  • Distinct jerking at maximum deviation
  • Angle of the eye upon jerking is 45 degrees or less from the center

If four or more signs of impairment exist between both eyes, then a person likely has a BAC over the legal limit of 0.08 percent. According to NHTSA research, the test is able to properly classify nearly 90 percent of suspects.

One-Leg Stand Test

For the One-Leg Stand test, DUI suspects must stand on one foot while keeping their other foot approximately six inches above the ground and counting aloud until an officer or examiner instructs them to put their foot back down. While administering the test, an officer tries to identify if a subject is displaying any of the four following indications of impairment:

  • Using arms to balance
  • Swaying while balancing
  • Putting a foot down
  • Hopping to keep balance

NHTSA research reveals that approximately 83 percent of people who show at least two of these impairment indicators will have a BAC over the legal limit.

Walk and Turn Test

Along with the One-Leg Stand test, the Walk and Turn test is a “divided attention” test, which can be easily performed by the majority of unimpaired people. In the Walk and Turn test, an individual is directed to walk in a straight line for nine steps by putting the heel of one foot directly in front of the toes of the other foot. After walking in a line for nine steps in this manner, a subject is then asked to turn around on one foot and continue the test by returning to their original position in the same fashion.

During the test, an examiner or officer tries to identify the following impairment indicators:

  • Loss of balance while receiving instructions
  • Beginning prior to the end of the instructions being given
  • Stopping to regain balance while walking
  • Stepping off of the line
  • Not touching the heel of one foot to the toe of the other
  • Using arms to balance
  • Taking the wrong number of steps
  • Making an improper turn

According to the NHTSA, 79 percent of people who show at least two of these indications of impairment will have a BAC over the legal limit.

Combination of Components

When these three SFST tests are combined, officers have been found to be accurate in more than 90 percent of cases involving DUI. However, in 1981, Moskowitz, Burns, and Tharp found the HGN was only accurate 77 percent of the time, the Walk and Turn was only accurate 68 percent of the time, and the One-Leg Stand was accurate 65 percent of the time. The trio of researchers also found that only 81 percent of arrest decisions were correct when combining all three measures. However, as previously mentioned, a 1998 study performed by Stuster and Burns found that arrest decisions based on Standardized Field Sobriety Test results were much more accurate.

To learn more about Pennsylvania DUI laws and procedures, including field sobriety tests, contact our experienced Pennsylvania criminal attorneys today.

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