Field Sobriety Tests

Breathalyzer

How Accurate are Field Sobriety Tests?

 Field sobriety tests are one of several factors officers use to determine if someone has been driving under the influence of alcohol.  Officers use the results of these tests to influence their decision as whether or not it’s necessary to administer more tests, namely, the breathalyzer test or a blood test.  The question at hand however, is how accurate are these tests and should they be used to determine if someone is intoxicated or not?

Firstly, it’s important to note that California has used the results of field sobriety tests since the 1970’s and the results are a significant piece of evidence used to determine if a driver is guilty of a DUI.  But some scientists are weary of the science used in developing these tests and question the ability of an officer to determine a driver’s sobriety based off their results.

Field sobriety tests are not mandatory!  If an officer has reasonable suspicion to believe that a driver has been drinking, namely through smelling alcohol on a driver’s breath or witnessing strange movements of the eyes, then the officer will ask if the driver is willing to take a field sobriety test.  If the driver does not wish to take the test, then the officer must proceed and the issue must be dropped.  However, if a driver refuses to take a field sobriety test that information will be noted and added to the officer’s report.  A driver has the right to refuses a field sobriety test but must take either a breathalyzer test or a blood test, but not both.

When someone receives a license in the state of California they give their consent to take either a breath, blood, or urine test to determine if they have been drinking.  If a driver refuses to take either a breath, blood, or urine test, then the driver will have their license suspended for one year and will be faced with fines.

Different Types of Field Sobriety Tests

There are four different types of field sobriety tests: balance tests, coordination tests, mental agility tests, and eye tests.  One of the most common types of field sobriety tests are the balance tests: walk-the-line, the walk-and-turn, one-leg stand, and “Rohmberg”.

The walk-the-line test is when an officer asks a subject to walk on a line, either painted or imaginary, and touch their left heel to their right toe and visa versa.  If the subject lifts an arm, or both arms and sways in any way then they’ve “failed” the test according to the arresting officer.

The walk-and-turn test is the most commonly used balance test in an officer’s repertoire.  An officer will ask a subject to walk from “here” to “there” and back again, either on a painted line or an imaginary line.  Again, if the subject lifts an arm, or both arms and sways in any way the subject has “failed” the test.

The one-leg stand, commonly referred to as the leg raise, is when an officer asks a subject to stand on one foot and lift the other foot approximately six inches off the ground for a certain amount of time.  Officer’s commonly say, “if you put your foot down, then lift it back up”.  However, if a subject places the lifted foot on the ground, sways, or lifts his or her arms they have “failed”.

The last type of balance test is the “Rohmberg” test, also referred to as the stand at attention test.  Subjects are asked to stand rigidly and let their heads fall back, if they sway in any way they have “failed” the test.

There are several problems with these tests that must be addressed.  Namely, the inability to sway while performing these test should not automatically lead to a subject failing.  There have been several studies claiming there is no correlation between alcohol and body swaying.  Secondly, a subject should not fail a test for merely lifting up one or both arms.  Lifting up our arms while balancing is a basic reaction to keeping our balance, so being asked to ignore our basic instincts while being tested poses a problem.  Should a subject be penalized for acting instinctually?  Another problem with the balance test results is whether or not the surface conditions were fair, if either uneven surfaces, loose pavement, angled streets, muddy or slippery surfaces were used during the test, the results might seem invalid.  The final flaw in the balance tests is in the instructions, part of the instructions for the one-leg stand is “if you put your foot down, then lift it back up” giving the subject the perception that it’s completely permissible to lower his or her foot, only to fail when doing so.

Dr. Spurgeon Cole, a retired Clemson University psychology professor has been quoted as saying, “It is designed to fail.  It’s designed to fail.  There are no norms, there is no average score.  We have no idea what the average person could do on the one leg with the heel to toe.”[1]  Dr. Cole also performed a test where he showed experienced officers videotapes of field sobriety tests and asked the officers if the subjects were above or below 0.10% BAC.  The officers were correct only 53% of the time.

The next type of field sobriety test is the coordination test.  The most common type of coordination test is the finger-to-nose test.  For this test an officer will will ask a subject to tip their head back and spread their arms and then touch the tip of their index finger to the tip of their nose, first with the right hand and then with the left.  If the subject performs this action too slowly then the subject has “failed” the test.  The main problem with this test is that often times the officer will not clarify that the test is timed so the subject presumes he or she has ample time to perform the action, but then “fails” because he or she performed them too slowly.

Mental agility tests are the next type of tests.  These test a subjects mental ability through the performance of seemingly easy tasks.  A subject can be asked to reverse count starting from a random digit, recite the alphabet starting with a random letter, or a subject will be asked to write the alphabet.  If a subject fails to do these in a timely manner with perfect execution then the subject will inevitably “fail”.  However, the stress of performing these tasks while under the watchful eye of a police officer can dramatically affect a person’s performance.

The last type of field sobriety tests are the eye tests.  The first type of eye test is the pupil reaction test.  During this test an officer will shine either a flashlight or a pen light into a subjects eyes and see how quickly their pupils dilate.  If an arrestee’s pupils dilate slower then the officer’s parter’s pupils dilate then they are considered intoxicated.  The other eye test is the gaze nystagmus test.  Nystagmus is defined as “rapid involuntary movements of the eyes” and for this test an officer will ask a subject to watch a pencil or pen with only their eyes.  The subject is not allowed to move his or her head back and forth, only their eyes.  The officer is looking for the angle at which the subjects eyes start moving rapidly in a jerking fashion.  If the angle is less than 45% it is reasonable to assume the subject is intoxicated and he or she has “failed the test”.  The problem with these tests are that they rely heavily on the officer’s assessments and readings.  If the officer is not sufficiently trained in either of these tests then the results can be misinterpreted.

The majority of DUI cases have arrestees perform two or three of the tests mentioned above.  The strongest cases against the results of the tests are:

  • The field sobriety tests were administered under difficult or stressful conditions.
  • The subject’s performance on the tests were influenced by physical ailments and emotional instability.
  • The officer’s analysis of the subjects results were biased.
  • The results of the tests were not recorded correctly.
  • The tests are not as easily performed by intoxicated or sober person’s alike.

Alcohol on the Breath

One of the signs that officers look for most when determining if a subject has been drinking is the smell of alcohol on the breath.  Smelling alcohol on a driver’s breath is enough evidence to ask a subject to perform the field sobriety tests mentioned above.  But what does alcohol on the breath really mean and how much can an officer learn from simply smelling it?

In 1999, Moskowitz, Burns and Ferguson performed a test with 20 experienced officers to see if they could distinguish among fourteen subjects with blood alcohol concentrations (BAC) ranging from 0.00% to 0.13% (the legal limit in California is 0.08% for most drivers).  The officers were also asked to distinguish beer, wine, bourbon or vodka on the subjects breath under optimal smelling conditions.  The results of the studies were extremely insightful, the officers could not distinguish between the various alcohol types nor could they estimate the BAC of the subjects beyond a guess.  The results of the study showed that when officers pull over a subject for suspicion of DUI they cannot determine what type of alcohol he or she has consumed, when he or she consumed the alcohol, or how much alcohol he or she has consumed; therefore, the smell of alcohol a driver’s breath cannot be the sole determinate for a DUI conviction.

If an officer smells alcohol on a driver’s breath that officer then has the right to ask the driver to perform a field sobriety test because their is reasonable doubt that the driver is under the influence

It’s important to note that beer and wine are the most pungent types of alcohol while simultaneously containing the smallest amount of alcohol by volume.  That being said, one can drink more beer and wine and expel a more pungent alcohol odor, while still being under the legal limit.

The Breathalyzer Test

If an officer pulls somebody over for suspicion of DUI, performs the field sobriety test and still believes the driver is intoxicated, then at that time the officer has the right to execute a breathalyzer test.  A breathalyzer test is used to prove a subject is guilty by measuring the amount of alcohol on a person’s breath.  Breathalyzer tests are administered to an arrestee at the spot of the crime.

Many states require that a subject needs to provide two samples.  The two samples must measure within 0.020 units of each other for the test to be considered properly administered.  If the two samples do not measure within 0.020 units of each other there can be speculation that either the instrument or the operator was working improperly.

There are several factors that can potentially alter a breathalyzer reading:

  • If the subject ate something prior to the test.
  • If the subject burped during the test.
  • If the subject used mouth care strips, tobacco, or an inhaler with 15 minutes of the test.
  • If the subject was exposed to acetone or is an uncontrolled diabetic.

It’s important to note that a subject is only required to take a breathalyzer test or give a blood sample, but not both.  Under some rare circumstances when both a subject’s breath and blood are not available then a urine test will suffice.  It is illegal for an officer to lead an arrestee in one direction over the other.  For instance, it has been recorded that some officers try to intimidate defendants into taking a breathalyzer test by claiming that he or she will sit in jail until the blood technician is available.  In actuality, some officers prefer breathalyzer tests because the results are more immediate.

On the other hand, officers have also been known to lead an arrestee to take a blood test because they are thought to be more accurate.  Either way, a subject is only required to give one sample and the decision as to which to give is completely up to the arrestee.  If an officer attempts to lead a defendant one way or the other then that can be used against the officer in court.

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References

[1] http://www.wsbtv.com/news/news/local/professor-dui-field-tests-designed-fail/nFdKg/

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