What Are Police Officers Looking for When They Administer Field Sobriety Tests?

The third phase of the DWI detection and investigation process is the pre-arrest screening. During this stage, a police officer, having reasonable suspicion that you were driving while intoxicated, might direct you to perform a few field sobriety tests (FSTs). The officer administers them to establish probable cause to arrest you, gathering evidence to support their belief that you were drunk driving.

Generally, officers administer what are referred to as Standardized Field Sobriety Tests (SFSTs). The National Highway Traffic Safety Administration has recognized three SFSTs as reliable and valid measures of intoxication: horizontal gaze nystagmus, walk and turn, and one-leg stand. To determine whether you are impaired, the officer will be looking at specific clues in each test.

If you have been accused of DWI in Minneapolis, please contact Brockton D. Hunter P.A. at (612) 979-1112.

What Are Police Officers Looking for with the Horizontal Gaze Nystagmus Test?

The horizontal gaze nystagmus (HGN), commonly referred to as the pen test, is a physiological response assessment. In other words, it’s testing your body’s reaction to a stimulus, specifically the involuntary jerking of the eyes (nystagmus) when the gaze moves in one direction or another.

The HGN works as follows:

  • The officer holds a small object (e.g., a pen, flashlight, or finger) about 12 inches from your nose
  • They will direct you to follow the stimulus with your eyes only (you cannot move your head)
  • They then move the object toward your right ear and hold it there for about 4 seconds
  • The officer then moves the object toward your left ear

When administering this assessment, the officer will be looking for three clues of intoxication:

  1. Your eyes jerk while tracking the stimulus
  2. Your eyes continue to jerk when the object is held at one side for 4 seconds
  3. The jerking movement begins before the stimulus gets to a 45-degree angle (note that the higher your blood alcohol concentration (BAC), the earlier the eye jerks will begin)

What Are Police Officers Looking for with the Walk and Turn Test?

The walk and turn (WAT) test is a divided attention assessment. It requires you to attend to two or more things simultaneously. Focusing on more than one stimulus is difficult for an intoxicated person.

The WAT has an instruction and performance phase.

During the instruction stage, the officer will tell you to:

  • Stand with your feet heel-to-toe
  • Keep your arms at your side
  • Stay in the position until they say you can start the test
  • When told to do so, take 9 heel-to-toe steps across a line in one direction, turn, and take 9 heel-to-toe steps in the other direction

After the officer gives you the instructions, they will have you begin the assessment.

The officer is looking for clues of intoxication during both the instruction and performance phases.

Indicators include:

  • Inability to balance while being given instructions
  • Starting the test before being told to do so
  • Stopping before getting to 9 steps in either direction
  • Having a gap of more than 1 inch when walking heel-to-toe
  • Not remaining on the line while walking
  • Raising arms to balance
  • Not making a proper turn
  • Taking more or less than 9 steps in either direction

What Are Police Officers Looking for with the One-Leg Stand Test?

Like the WAT, the one-leg stand (OLS) test is a divided attention assessment with an instruction and performance phase.

The officer will give you the following instructions:

  • Stand with your feet together
  • Keep your arms at your side
  • When told to do so, raise one foot about 6 inches off the ground
  • Look at your raised foot while counting out loud
  • Continue counting until told to stop

The officer will then have you begin the assessment. They will observe your behavior at both the instruction and performance stages.

The clues indicating intoxication with the OLS include:

  • Unable to keep balanced
  • Raising arms to balance
  • Hopping
  • Dropping the elevated foot

Are the SFSTs Reliable?

As noted earlier, the NHTSA recognizes the SFSTs as valid and reliable. That means the assessments have been studied rigorously, with results indicating that poor performance suggests intoxication.

According to the NHTSA, the SFSTs have the following accuracy ratings:

  • HGN: 88%
  • WAT: 79%
  • OLS: 83%

Police officers go through a 24-hour Standardized Field Sobriety Testing course (also referred to as a DWI detection course). The course trains the officers to administer the SFSTs and recognize clues of intoxication.

Although the SFSTs are valid and officers are taught how to conduct them, that does not mean that the results are 100% accurate 100% of the time.

Several factors can affect performance on them, including, but not limited to:

  • Health conditions or injuries
  • Nerves
  • Clothing or footwear
  • External distractions
  • Improper instructions
  • Environment

Therefore, even though you might have been completely sober, the officer might have observed indicators of intoxication because the conditions were less than ideal or a non-alcohol-related variable caused you to fail.

Can I Refuse to Participate in FSTs?

Legally, you do not have to participate in FSTs. You can politely refuse, and the officer would have to forego the assessment. Additionally, you can’t face penalties for not performing in the tests.

Still, even though you were not subject to FSTs, the officer might still have grounds to arrest you. They may rely on other evidence to establish probable cause to take you into custody.

Is It Bad If I Took the FSTs?

If you’re pulled over on suspicion of DWI, it can be difficult to say no to a police officer when they direct you to do something, especially if they make it feel as if you don’t have a choice in the matter. Thus, you might have complied with an order to perform in the FSTs.

Although it may be in your best interest to refuse to take the FSTs, participating in them is not necessarily bad. Depending on your situation, it may be possible to challenge the evidence the police collected against you.

Contact Brockton D. Hunter P.A. for DWI Defense

Our Minneapolis attorneys have extensive experience fighting DWI charges. Whether or not you participated in the FSTs, we can evaluate your case and determine your legal options for challenging the allegations against you.

Schedule a free consultation with us by calling (612) 979-1112 or submitting an online contact form today.