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Field Sobriety Test in California

Field Sobriety Tests (FSTs) and Standardized Field Sobriety Tests (SFST) are a battery of tests an officer will likely administer if a driver is suspected of driving under the influence of alcohol or drugs. FSTs are a series of instructions an officer can provide to a subject that will allow the officer to observe objective signs of impairment due to alcohol or drugs.

What are FSTs used for?

The 4th amendment of the US Constitution requires an officer have probable cause before making an arrest. An officer usually develops probable cause by conducting an investigation recording the results. That is why police officers often record encounters with audio and visual recorders and take notes for their police report. The purpose of the FSTs are provide the officer with tangible evidence of your impairment due to alcohol that will justify the arrest, at which California's Implied Consent Law will be invoked, and provide evident to be presented in court against you.

The FSTs are also an opportunity for the officer to make observations of the subject. Often police reports will make reference to swaying of the subject, slurred speech, odor of alcohol, ability to understand and repeat directions, etc. FSTs require a person to understand and perform multiple tasks simultaneously to simulate the multi-tasking required to operate a motor vehicle. This will give the officer an indication of whether a subject can safely operate a vehicle.

What FSTs will an officer likely use?

Law enforcement personnel are typically trained to administer a wide range to tests to determine impairment caused by alcohol.  

Standardized Field Sobriety Test (SFST)

The US National Highway Traffic Safety Administration (NHTSA) has determined the scientific reliability of three tests which are the horizontal gaze nystagmus test, the walk-and-turn test, and the one-leg-stand test.

Horizontal Gaze Nystagmus Test (HGN) 

This test requires a subject to follow an object, usually a pen, with their eyes without rotating their head.  The officer moves the pen 45 degrees to the left and right.  The officer is looking for the following indicators: lack of smooth pursuit, nystagmus (involuntary movement) of the eyes at maximum deviation, and nystagmus prior to the maximum deviation.  This test is 77 percent accurate in determining if a subject has a blood alcohol concentration is above .10 percent.  

HGN must be administered in accordance the NHTSA guidelines or the results may be invalidated.  The object cannot be moved to fast or to slow.  The officer must hold the object at the maximum deviation for at least 4 seconds.  The object must be held between 12 inches and 15 inches from the subjects face.  Failure to adhere to these strict guideline leaves the officer open to challenge in court.

Walk-and-Turn Test

This test involves walking heel-to-toe for a set number of steps.  This is testing a subjects physical and mental abilities while following specific instructions.  The NHTSA Student Manual places the reliability at 68 percent for predicting if a subjects blood alcohol concentration is above .10 percent.

The walk-and-turn test has significant issues.  An uneven surface including small debris will impact the results.  Medical conditions unrelated to alcohol such as spine or knee issues will prevent a subject from performing well.  This test is typically performed on the side of a road where bright lights, load traffic, and wind may impact the subject.  If the subject is wearing inappropriate shoes or clothing their ability to perform will be impacted.

The One-Leg-Stand Test

This test requires the subject to lift one leg while balancing, count to 30 seconds.  The subject must keep their arms at their side.  The officer is looking for swaying, placing foot down, use of arms for balance, and hopping.  The NHTSA Student Manual places the reliability at 65 percent for predicting if a subjects blood alcohol concentration is above .10 percent.

Several factors may impact the results of the test.  Performance on an Uneven surface, improper timing by the police officer, medical conditions, improper clothing or shoes, and distractions in the environment.

Non-Standardized Field Sobriety Tests (FST)

While only SFSTs have been verified as scientifically reliable by the NHTSA, law enforcement personnel routinely administer FSTs to a subject as part of their investigation for a suspected DUI.  There are a wide variety of tests officers are trained to administer.  Here is a list of the most common:

Rhomberg Test - requires a suspect to tilt their eyes closed and head back and estimate when 30 seconds have elapsed.
Finger to Nose Test - requires a suspect attempts to touch the tip of their nose with the their fingertip while standing with their eyes closed and head tilted back.
Finger Count Test - requires a suspect to touch their thumb to each finger while counting and reversing the process.

FST are easier to challenge in most cases because they lack the scientific reliability of SFST as indicators of alcohol related impairment.  Most of these tests require superb dexterity but a lack of dexterity can be explained by many medical conditions a suspect may be experiencing at the time.

If you have been arrested for supected DUI, you likely were asked to perform SFSTs and FSTs.  An experienced attorney can review the evidence and challenge the officer's findings  The Law Offices of Steven McNicholl has that experience and will get you through your case in the best shape possible.

See also

VC 23152(a) Driving under the Influence

VC 23152(b) DUI with BAC of .08% or above

VC 23153(a) DUI causing injury

VC 23152(b) DUI causing injury with BAC of .08% or more

VC 23136 Underage Driving Under the Influence BAC .01% or more

PC 191.5(a) Gross Vehicular Manslaughter with gross negligence

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