The law enforcement officer who stops you for a DUI suspicion needs probable cause to be able to arrest you. There are a few ways in which the officer can obtain probable cause. One of them is any admissions of guilt given by the driver. Second are officer’s observation of the suspect’s looks, behavior, bearing and speech. Field sobriety tests (FSTs) are the third way.

These tests can be administered in a few different ways, which have been standardized by National Highway Traffic Safety Administration (NHTSA). The officer can ask you to submit to these if they feel it necessary. These tests are said to examine “divided attention” capacity, which is essential to driving – for example, when you need to pay attention to road signs and continue driving properly and safely.

Horizontal Gaze Nystagmus (HGN)

Of the three types of FSTs, this is the most accurate one. The officer asks the driver to follow an object as they move it from side to side. The officer pays attention to the movements of the driver’s eyeballs. If they jerk or bounce, that gives them probable cause to suspect the driver is intoxicated with alcohol or drugs.

Walk and turn (WAT)

This test is the second in accuracy of the three. The testee has to walk in a straight line for nine heel-to-toe steps. After nine such steps, the suspect should turn and walk back to the starting point in the same manner. If the person falters, lurches, is incapable of keeping balance, starts too early or doesn’t stick to the instructions, the officer has justification to arrest them.

One leg stand (OLS)

This test is the least accurate of all. It is required that the officer demonstrate this test to the driver. The suspect should stand with feet one next to another and their arms next to their body. Then they should lift one leg and count upwards of 1000 while they are looking at the raised foot.

Contesting field sobriety tests

The law enforcement officer is required to follow set procedures when administering field sobriety tests. There are certain conditions that have to be met. For example, for the HGN the suspect can’t have any medical issues with the eyes. For WAT and OLS the surface should be hard and dry. The suspect should be offered to remove their shoes if their heels are higher than 2 inches. There are also medical conditions that could invalidate these tests. Another critical point is whether the officer clearly instructed the driver how the test is to be performed.

The officer’s failure to conform to the procedures of FST administration could result in a dismissal of the test results and thus, elimination of probable cause.

Last point is that results of these tests are highly subjective and can usually be challenged.

Hire a reputable DUI lawyer in San Diego

If you are charged with DUI in California, an experienced and reputable DUI attorney can assist you in getting the best possible outcome in your DUI case. California DUI laws are pretty harsh and a professional can best navigate the court procedures and processes. If you are looking for a DUI lawyer in San Diego, the attorneys at San Diego DUI Pros are always here for you. Feel free to call us for a no-cost, pressure-free consult regarding your case. Our DUI lawyers are aggressive, experienced and ethical. Don’t hesitate – contact us right away!