DWI DETECTION GUIDE
Weaving plus any other cue: p = at least .65
Any two cues: p = at least .50
Problems Maintaining Proper Lane Position
p=.50.75
Weaving, Weaving across lane lines, Straddling a lane line, Swerving,
Turning with a wide radius, Drifting, Almost striking a vehicle or other
object
Speed and Braking Problems
p=.45.70
Stopping problems (too far, too short, or too jerky), Accelerating or
decelerating for no apparent reason, Varying speed, Slow speed (10+ mph
under limit)
Vigilance Problems
p=.55.65
Driving in opposing lanes or wrong way on one-way, Slow response to traffic
signals, Slow or failure to resond to officer's signals, Stopping in lane
for no apparent reason, Driving without headlights at night*, Failure to
signal or signal inconsistent with action*
Judgment Problems
p=.35.90
Following too closely, Improper r unsafe lane change, Illegal or improper
turn (too fast, jerky, sharp, etc.), Driving on other than the designated
roadway, Stopping inappropriately in response to officer, Inappropriate
or unusual behavior (throwing, arguing, etc.), Appearing to be impaired
POST STOP CUES
p > .85
- Difficulty with motor vehicle controls
- Difficulty exiting the vehicle
- Fumbling with driver's license or registration
- Repeating questions or comments
- Swaying, unsteady, or balance problems
- Leaning on the vehicle or other object
- Slurred speech
- Slow to respond to officer/officer must repeat
- Provides incorrect information, changes answers
- Odor of alcoholic beverage from the driver
- p > .50 when combined with any other cue:
- Driving without headlights at night
- Failure to signal or signal inconsistent with action
The probability of detecting DWI by random traffic enforcement stops
at night has been found to be about three percent (.03).
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