DWI Detection PhasesDWI Detection Phases

Vehicle in MotionVehicle in Motion Initial observation of Initial observation of

vehiclevehicle Observation of stopping Observation of stopping

sequencesequence

Personal ContactPersonal Contact Observation of driverObservation of driver Observation of exitObservation of exit

Pre-Arrest ScreeningPre-Arrest Screening Standardized Field Standardized Field

Sobriety TestsSobriety Tests PBTPBT

Standardized Field Sobriety TestsStandardized Field Sobriety Tests

Designed to evaluate a persons divided Designed to evaluate a persons divided attention abilityattention ability

Three Standardized Field Sobriety TestsThree Standardized Field Sobriety Tests Horizontal Gaze NystagmusHorizontal Gaze Nystagmus Walk and TurnWalk and Turn One Leg StandOne Leg Stand

Horizontal Gaze Nystagmus (HGN)Horizontal Gaze Nystagmus (HGN)

Three Standardized CluesThree Standardized Clues Lack of Smooth PursuitLack of Smooth Pursuit Distinct and Sustained Nystagmus at Distinct and Sustained Nystagmus at

Maximum DeviationMaximum Deviation Onset of Nystagmus Prior to 45 DegreesOnset of Nystagmus Prior to 45 Degrees

3 Clues x 2 Eyes=6 Possible Clues3 Clues x 2 Eyes=6 Possible Clues

HGN ValidityHGN Validity

If FOUR or more clues are observed, the If FOUR or more clues are observed, the percentage of accuracy of the subject percentage of accuracy of the subject have a BAC of 0.08 or more is have a BAC of 0.08 or more is 88%88%

1997 San Diego Field Validation Study1997 San Diego Field Validation Study

Walk and Turn TestWalk and Turn Test

Instruction Stage (2 Clues)Instruction Stage (2 Clues) Walking Stage (6 Clues)Walking Stage (6 Clues)

Walk and Turn CluesWalk and Turn Clues

Eight Standardized CluesEight Standardized Clues Can’t Balance During the InstructionsCan’t Balance During the Instructions Starts Too SoonStarts Too Soon Steps Off the LineSteps Off the Line Uses Arms for Balance (More than 6”)Uses Arms for Balance (More than 6”) Fail to Touch Heel to Toe (More than ½”)Fail to Touch Heel to Toe (More than ½”) Stops While WalkingStops While Walking Improper Turn/Lost Balance on TurnImproper Turn/Lost Balance on Turn Incorrect Number of StepsIncorrect Number of Steps

Walk and Turn ValidityWalk and Turn Validity

TWO or more clues indicates a BAC at or TWO or more clues indicates a BAC at or above 0.08 with an accuracy of above 0.08 with an accuracy of 79%79%

1997 San Diego Field Validation Study1997 San Diego Field Validation Study

One Leg Stand TestOne Leg Stand Test

Instruction StageInstruction Stage Balance and Counting StageBalance and Counting Stage

One Leg Stand CluesOne Leg Stand Clues

SwayingSwaying Uses Arms For Balance (More Than 6”)Uses Arms For Balance (More Than 6”) HoppingHopping Puts Foot DownPuts Foot Down

*Persons over 65 years of age or more than 50 pounds *Persons over 65 years of age or more than 50 pounds over weight may have difficulty with testover weight may have difficulty with test

One Leg Stand ValidityOne Leg Stand Validity

TWO or more clues indicates a BAC of TWO or more clues indicates a BAC of 0.08 or more with an accuracy of 0.08 or more with an accuracy of 83%83%

1997 San Diego Field Validation Study1997 San Diego Field Validation Study

Other Field Sobriety TestsOther Field Sobriety Tests

NOT Validated But Still Excellent Sources NOT Validated But Still Excellent Sources to View Impairmentto View Impairment

ExamplesExamples Romberg BalanceRomberg Balance Finger to NoseFinger to Nose AlphabetAlphabet CountingCounting