Law Enforcement Caselaw and Statutes: The Legal Environment DWI Detection and Standardized Field Sobriety Testing

Session 3 – The Legal Environment

DWI Detection and Standardized Field Sobriety Testing

• Continue to rely on your detection

training and experience

• When making a DWI arrest assume

chemical tests will not be available

• Present your observations clearly

• Thorough documentation is critical

Illegal Per Se Summary

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Illegal Per Se Summary

Police officers dealing with impaired drivers must continue to rely primarily on their own

training and experience in detection to determine whether an arrest should be made.

Usually it is impossible to obtain a legally admissible chemical test result until after the

arrest has been made. Sometimes drivers will refuse the chemical test after they have

been arrested. Then the case will depend primarily upon the officer's observations and

ability to articulate their testimony. When making a DWI arrest, always assume that the

chemical test evidence will not be available. It is critical that you organize and present

your observations and testimony in a clear and convincing manner. This will allow more

impaired drivers to be convicted regardless of whether they take the chemical test(s) or

the test(s) results.

Session 3 – The Legal Environment

DWI Detection and Standardized Field Sobriety Testing

Laws and Presumptions

• “Under the influence” is difficult to prove

• State statutes vary

Implied Consent

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C. Implied Consent Law and Presumptions

Description

It is not completely clear to what degree the level of impairment equates to driving while

under the influence. Some courts have held that the slightest degree of impairment in

the ability to drive means the driver is "under the influence." Other courts have held that

there must be evidence of substantial impairment of the ability to drive before a DWI

conviction is warranted. Therefore, proving that a driver was "under the influence" has

been (and continues to be) difficult.

To help resolve this difficulty, states have enacted implied consent laws. The principal

purpose of the implied consent law is to encourage people arrested for DWI to submit to

a chemical test to provide scientific evidence of alcohol influence.

Notes:_______________________________________________

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Notes:_______________________________________________

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HS 178 R5/13 8 of 29

Session 3 – The Legal Environment

DWI Detection and Standardized Field Sobriety Testing

• Operates or controls motor vehicle

• Upon state public highways

• Driver must consent to chemical test to

determine blood alcohol and/or drug

content

• When arrested for acts committed while

operating under the influence of alcohol

and/or any drug

Key Features of Implied Consent

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The implied consent law usually includes language similar to “Any person who”:

• Operates or is in actual physical control of a motor vehicle

• Upon the public highways of this state

• Shall be deemed to have given consent to a chemical test for the purpose of

determining the alcohol and/or drug content of that person’s blood

• When arrested for any acts alleged to have been committed while the person was

operating or in actual physical control of a vehicle while under the influence of alcohol

and/or any drug.

The implied consent law states drivers must submit to a chemical test(s). The law

provides penalties for refusal to submit to the test. The law also provides that the

individual's driver's license may be suspended or revoked if the refusal is found to be

unreasonable. The purpose of the implied consent law is to encourage those arrested

for DWI to submit to a chemical test so that valuable evidence may be obtained.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 9 of 29

Session 3 – The Legal Environment

DWI Detection and Standardized Field Sobriety Testing

BAC _____or more

• Presumed under the influence

Less than _____

• Presumed not under the influence

At least _____ but below _____

• No presumption

Legal Presumptions

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Legal presumptions define the significance of the scientific chemical test evidence.

Usually the implied consent law provides an interpretation or presumption for the

chemical test evidence like the following, for example:

If the chemical test shows that the person's blood alcohol concentration (BAC) is .08 or

more it shall be presumed that the person is under the influence.

In some states – If the test shows that the BAC is _____ or less, it shall be presumed

that the person is not under the influence.

If the test shows that the BAC is more than but less than , there is no

presumption as to whether the person is or is not under the influence. The weight of the

chemical test evidence is presumptive of alcohol influence, not conclusive.

The court may accept the legal presumption and conclude that the driver was or was

not impaired on the basis of the chemical test alone. However, other evidence such as

testimony about the defendant’s driving, odor of alcohol, appearance, behavior,

movements, speech, etc. may be sufficient to overcome the presumptive weight of the

chemical test.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 10 of 29

Session 3 – The Legal Environment

DWI Detection and Standardized Field Sobriety Testing

Is it possible for a person whose BAC is

above the state’s per se or presumptive

level to be acquitted of DWI?

Example Number 1

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It is possible for a person whose BAC at the time of arrest is above the per se or

presumptive level legal limit to be acquitted of DWI. It is also possible for a person

whose BAC at the time is below the per se or presumptive level to be convicted of DWI.

Consider the following examples:

Example 1

A driver is arrested for DWI. A chemical test administered to the driver shows a BAC of

0.13. At the subsequent trial, the chemical test-evidence is introduced. In addition, the

arresting officer testifies about the defendant’s driving, appearance and behavior. The

testimony is sketchy, confused and unclear.

Another witness testifies that the driver drove, behaved and spoke normally. The court

finds the defendant not guilty of DWI.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 11 of 29

Session 3 – The Legal Environment

DWI Detection and Standardized Field Sobriety Testing

Is it possible for a person whose BAC was

below the state’s per se or presumptive

level to be convicted of DWI?

Example Number 2

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Example 2

A driver is arrested for DWI. A chemical test administered to the driver shows a BAC of

0.05. At the subsequent trial, the chemical test evidence is introduced. In addition, the

arresting officer testifies about the defendant’s driving, odor of alcohol, appearance,

slurred speech, and inability to perform divided attention field sobriety tests. The

testimony is clear and descriptive. The court finds the defendant guilty of DWI.

The difference in outcomes in the two examples cited is directly attributable to how well

the arresting officer articulates the evidence other than the chemical test. Remember

that the chemical test provides presumptive evidence of alcohol influence; it does not

provide conclusive evidence. While the "legal limit" in a given jurisdiction may be 0.08

BAC, many people will demonstrate impaired driving long before that "legal limit" is

reached.

Session 3 – The Legal Environment

DWI Detection and Standardized Field Sobriety Testing

Chemical test evidence is presumptive, not

conclusive

Key Point

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Summary point: The chemical test provides presumptive evidence of alcohol influence,

but does not provide conclusive evidence.

Notes:_______________________________________________

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Notes:_______________________________________________

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HS 178 R5/13 12 of 29Source: DWI Detection and

Standardized Field

Sobriety Testing

Law Enforcement Caselaw and Statutes

October 27, 2015

The Legal Environment DWI Detection and Standardized Field Sobriety Testing

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