Evaluation Factors Flashcards

When using the SFST battery to detect drug impairment (rather than alcohol), which test in the standard battery is considered LEAST reliable as a standalone indicator?

Answer: HGN, because some drug categories do not produce nystagmus

HGN is most specifically linked to alcohol and certain drug categories; stimulants or cannabis alone may not reliably produce nystagmus, making it the least universal drug indicator.

A suspect scores 2 clues on the One-Leg Stand. According to NHTSA research, what does this suggest?

Answer: The suspect is likely at or above 0.08% BAC

NHTSA research indicates that 2 or more clues on the One-Leg Stand suggests BAC at or above 0.08%, with approximately 83% accuracy.

Which of the following best describes the role of SFSTs in the overall DUI investigation?

Answer: SFSTs provide standardized, validated data to support probable cause for arrest

SFSTs are investigative tools that provide structured, research-backed observations to help officers establish probable cause; they are one component of a complete DUI investigation.

An officer notices that a suspect's eyes exhibit nystagmus only prior to 45 degrees during HGN. This observation most likely indicates:

Answer: A very high BAC or significant CNS impairment

Nystagmus onset before 45 degrees is associated with higher BAC levels; the earlier the onset angle, the greater the level of suspected impairment.

What is the minimum recommended distance between the suspect's eyes and the HGN stimulus during the test?

Answer: 12 to 15 inches

NHTSA recommends holding the stimulus 12 to 15 inches from the suspect's face to ensure proper eye tracking without causing strain.

How does alcohol impairment specifically affect the onset angle of nystagmus during HGN?

Answer: Higher BAC causes nystagmus to onset at a smaller angle (closer to center)

As alcohol impairs the brain's ability to control eye muscle movement, nystagmus begins earlier in the lateral range of motion, resulting in a smaller onset angle.

During the Walk-and-Turn, if a suspect steps off the line and then immediately steps back on and continues, the officer should:

Answer: Score the 'steps off line' clue and continue observing the remainder of the test

Any observable step off the line is scored as a clue regardless of whether the suspect self-corrects; the test continues to completion.