October 27, 2015

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.
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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.
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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.
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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.
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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.
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HS 178 R5/13 12 of 29Source: DWI Detection and
Standardized Field
Sobriety Testing

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