When Are Chemical Tests Required?
In Colorado, the officer must establish probable cause before they can arrest you
and require you submit to a
chemical test. The most common form of establishing probable cause is through the performance
and evaluation of voluntary roadside maneuvers, also known as Standardized Field
Sobriety Tests. These tests were developed and formulated by the National Highway
Traffic Safety Administration (NHTSA) and have been adopted throughout the country.
These tests are designed to detect impairment due to alcohol consumption.
Understanding SFSTs
The Denver DUI lawyers
at The Orr Law Firm are NHTSA certified in Standardized Field Sobriety Testing as
instructors. This training is very similar to what Colorado law enforcement receives
in order to be certified in SFSTs. There are around a dozen or so maneuvers that
are used by local law enforcement to determine impairment and/or intoxication; however,
there are three standardized tests that are most commonly used in Colorado.
The Standardized Field Sobriety Test (SFST) is a group of three standardized tests
that law enforcement officers perform on an individual to determine if that individual
has valid indicators of being impaired or if there is probably cause for arrest.
The tests are based on research conducted by the Southern California Research Institute
and were sponsored by the National Highway Traffic Safety Administration (NHTSA).
The following three tests compose the SFSTs:
- Horizontal Gaze Nystagmus (HGN)
- Walk-and-Turn (WAT)
- One-Leg Stand (OLS)
HGN Testing
Horizontal gaze nystagmus is an involuntary jerking of the eye that occurs naturally
as the eyes gaze to the side. Under normal circumstances, nystagmus occurs when the
eyes are rotated at high peripheral angles. However, when a person is impaired by
alcohol, nystagmus is exaggerated and may occur at lesser angles. An alcohol-impaired
person will also often have difficulty smoothly tracking a moving object.
In the HGN test, the officer observes the eyes of a suspect as the suspect follows
a slowly moving object such as a pen or small flashlight, horizontally with his or
her eyes. The examiner looks for three indicators of impairment in each eye: if the
eye cannot follow a moving object smoothly, if jerking is distinct when the eye is
at maximum deviation, and if the angle of onset of jerking is within 45 degrees of center.
NHTSA research found that this test allows proper classification of approximately
88 percent of suspects with BAC’s of .08 or greater (Stuster and Burns, 1998). However,
there are many forms of nystagmus, and nystagmus is a fairly common medical condition
that exists in thousands of people who are not impaired and have not consumed alcohol
or drugs. You do not have to be impaired or under the influence to have nystagmus.
Walk and Turn
The Walk-and-Turn test and One-Leg Stand test are "divided attention" and "balancing"
tests. In the Walk-and-Turn test, an individual is told to take nine steps, heel-to-toe,
along a straight line. After taking the steps, the suspect must turn on one foot
and return in the same manner in the opposite direction.
The examiner looks for these eight indicators of impairment:
- If the suspect loses balance while walking
- Begins walking before the examiner has finished giving instructions
- Stops to regain balance
- Does not touch heel-to-toe
- Steps off the line
- Uses arms to balance
- Makes an improper turn
- Takes an incorrect number of steps
NHTSA research indicates that 79 percent of individuals who exhibit two or more indicators
in the performance of the test will have a BAC of 0.08 or greater (Stuster and Burns,
1998). However, this test is not as simple as it seems. The officer oftentimes attempts
to deceive or trick the subject by giving incomplete or inconsistent instructions.
People who are not impaired may have difficulty performing this test if they have
certain medical conditions, equilibrium or balancing issues or are overweight.
One Leg Stand
The Walk-and-Turn test and One-Leg Stand test are "divided attention" and "balancing"
tests. In the One-Leg Stand test, the suspect is instructed to stand with one foot
approximately six inches off the ground and count aloud by thousands (One thousand-one,
one thousand-two, etc.) until told to put the foot down. The officer times the subject
for 30 seconds.
The officer looks for four indicators of impairment, including:
- Swaying while balancing
- Using arms to balance
- Hopping to maintain balance
- Putting the foot down
NHTSA research indicates that 83 percent of individuals who exhibit two or more such
indicators in the performance of the test will have a BAC of 0.08 of greater (Stuster
and Burns, 1998). Once again this test is not as simple as it sounds. A lot of people
who are not impaired will struggle to balance on one leg for 30 seconds. Overweight
subjects, people with medical conditions and equilibrium issues and weather conditions
can and will impact the performance of subjects on this test.
What Is the Overall Reliability of These Tests?
NHTSA claims that when all three tests are combined the overall efficiency at identifying
BACs
above .08 is 91 percent. These numbers are very misleading, as they assume the tests
were performed correctly by the officers in ideal weather and roadside conditions
with subjects who do not have any possible medical conditions that could explain
false positives or reasons for poor performance other than intoxication.
NHTSA is relying upon a study that has not even come close to meeting the scientific
standards set forth for all other studies to be considered valid. These studies have
not been peer reviewed, the subjects were not random, the study was not a double-blind
study, etc.
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