Field Sobriety Tests

Denver DUI Attorney

Field Sobriety Tests are generally conducted by trained police officers to help determine a person's blood alcohol content or sobriety. But these routine field sobriety tests may not be as accurate as they seem and most people can't perform these tests even when they are completely sober.

The three tests most commonly used by police are:

• The Horizontal Gaze Nystagmust test
• The Walk and Turn Test
• The One Legged Stand Test

The Horizontal Gaze Nystagmus Test (HGN)

Nystagmus is the involuntary eye movement that causes trembling or jerking. It is characterized by alternating smooth pursuit in one direction and rapid jerking in the other direction.

To conduct the test, the officer positions a light or an item 12-15 inches away from the driver's face and slowly moves the object from side to side. The officer is trained to check for any signs of involuntary movement or signs of nystagmus. If your eyes begin to jerk prior to reaching 45 degrees, the officer can use that as a clue that you have may have a blood alcohol level of more then .05%.

Even though the horizontal gaze nystagmus test is deemed the most reliable of all three tests at 77% accuracy, it still leaves room for error. This depends on the proper administration, proper scoring, and proper training received by the officer. While it is true that alcohol can cause nystamus, there are several other causes of nystagmus that have nothing to do with alcohol consumption such as: bodily or neurological disorders, medications and some prescription drugs, excessive amounts of caffeine or nicotine, head trauma and many others.

The Walk and Turn Test

The walk and turn test is commonly referred to as a Divided Attention Test because it divides the suspect's attention between mental and physical tasks.

The officer is required to conduct this test on a dry, hard, non slippery surface with sufficient room for the suspect to walk. The conditions of the area must be in no danger to the person if he or she were to fall.

When conducting the walk and turn test, the suspect is instructed to complete nine heel-to-toe steps on a visible line or walk parallel to a curb. From a distance the officer will try to observe any hints or clues of intoxication such as:

• Walking off the line
• Starting before instructions are finished
• Heel and toe not touching
• Stopping while walking
• Improper Turning
• Incorrect Number of steps

The walk and turn test is known to be less accurate in determining blood alcohol content over .08% than the Horizontal Gaze Nystagmus Test. Weather conditions can affect the validity of the test. People with disabilities, physical impairments, old age and overweight can have a hard time performing the test correctly.

One Legged Stand Test

The one legged stand test is the least reliable of the three. In order to perform this test, it is required to be performed on a level, dry and non slippery surface. The suspect will be instructed to raise one foot while counting out loud for as many as thirty seconds.

When performing this test, the officer must be at least three feet away and remain motionless as possible to not interfere with the suspect. From a distance the officer will observe for any clues of intoxication such as:

• Swaying while balancing
• The use of arms for balance
• Hopping on one foot to maintain balance
• Unable to maintain posture

People who have physical disabilities, overweight and are old of age can have a difficult time performing the tasks required. Weather or wind conditions can also affect the validity of the test.