DWI Detection and Standardized Field Sobriety Testing Session 5 – Phase One: Vehicle in Motion Phase One: Vehicle in Motion

DWI Detection and Standardized Field Sobriety Testing

Session 5 – Phase One: Vehicle in Motion

Phase One: Vehicle in Motion

Initial Observation

of the Vehicle

in Operation

?

5-3

A. Overview: Tasks and Decision

Your first task in Phase One: Vehicle in Motion is to observe the vehicle in operation to

note any initial cues of a possible DWI violation. At this point you must decide whether

there is reasonable suspicion to stop the vehicle, either to conduct further investigation

to determine if the driver may be impaired, or for another traffic violation. You are not

committed to arresting the driver for DWI based on this initial observation, but rather

should concentrate on gathering all relevant evidence that may suggest impairment.

Your second task during phase one is to observe the manner in which the driver

responds to your signal to stop, and to note any additional evidence of a DWI violation.

The first task, observing the vehicle in motion, begins when you first notice the vehicle,

driver or both. Your attention may be drawn to the vehicle by such things as:

• A moving traffic violation

• An equipment violation

• An expired registration or inspection sticker

• Unusual driving actions, such as weaving within a lane or moving at a slower than

normal speed

• Evidence of drinking or drugs in vehicle

If this initial observation discloses vehicle maneuvers or human behaviors that may be

associated with impairment, you may develop an initial suspicion of DWI.

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HS 178 R5/13 3 of 19

DWI Detection and Standardized Field Sobriety Testing

Session 5 – Phase One: Vehicle in Motion

Phase One: Vehicle in Motion

Initial Observation

of the Vehicle

in Operation

Observation of

the Stop

Should I Stop

the Vehicle? ?

5-4

Based upon this initial observation of the vehicle in motion, you must decide whether

there is reasonable suspicion to stop the vehicle. At this point you have three choices:

• Stop the vehicle.

• Continue to observe the vehicle.

• Disregard the vehicle.

Alternatives to stopping the vehicle include:

• Delaying the stop/no stop decision, in order to continue observing the vehicle

• Disregarding the vehicle

Whenever there is a valid reason to stop a vehicle, the officer should be alert to the

possibility that the driver may be impaired by alcohol and/or other drugs.

Once the stop command has been communicated to the suspect driver, the officer must

closely observe the driver's actions and vehicle maneuvers during the stopping

sequence.

DWI Detection and Standardized Field Sobriety Testing

Session 5 – Phase One: Vehicle in Motion Phase One:

Vehicle in Motion (Cont.)

Initial Observation

of the Vehicle

in Operation

Observation of

the Stop

Should I Stop

the Vehicle? ?

5-5

Sometimes, significant evidence of alcohol influence comes to light during the stopping

sequence. In some cases, the stopping sequence might produce the first suspicion of

DWI. Drivers impaired by alcohol and/or other drugs may respond in unexpected and

dangerous ways to the stop command.

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DWI Detection and Standardized Field Sobriety Testing

Session 5 – Phase One: Vehicle in Motion

Common Symptoms of

Alcohol Influence

Blood Alcohol Concentration

Impaired

Vision

0.08

Poor

Coordination

0.10

Slowed

Reaction

0.03

Impaired

Judgment

0.05

5-6

B. Initial Observations: Visual Cues of Impaired Vehicle Operation (Automobiles)

Drivers who are impaired frequently exhibit certain effects or symptoms of impairment.

These include:

• Slowed reactions.

• Impaired judgment as evidenced by a willingness to take risks.

• Impaired vision.

• Poor coordination.

DWI Detection and Standardized Field Sobriety Testing

Session 5 – Phase One: Vehicle in Motion

Common Symptoms of

Alcohol Influence (Cont.)

Blood Alcohol Concentration

Impaired

Vision

0.08

Poor

Coordination

0.10

Slowed

Reaction

0.03

Impaired

Judgment

0.05

5-7

This unit focuses on alcohol impairment because research currently provides more

information about the effects of alcohol on driving than it does about the effects of other

drugs on driving. Remember that whether the driver is impaired, the law enforcement

detection process is the same, and the offense is still DWI.

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HS 178 R5/13 5 of 19