I've just watched this video of a police officer in Miami administering a field sobriety test on a person suspected to be driving under the influence. The test takes over ten minutes.

There are two confusions I have. The first one is that, as I've learned on Wikipedia the whole point of the test is to establish probable cause for which to arrest someone. As you could see from the video this takes so much time, and the instructions aren't very clear for someone performing this for the first time. Would a breathalyser test not also establish probable cause?

Also, as I've seen on Wikipedia there is controversy over the use of such tests, and rightly so, as there have been studies that have shown how accurate or useful they are:

"After viewing the 21 videos of sober individuals taking the standardized field tests, the police officers believed that forty-six percent of the individuals had 'too much to drink'".

And there are other studies of the same sort.

Finally, I'm of the opinion that many who have never touched alcohol would fail this test for reasons such as that some tasks are quite demanding, the mental stress and intimidation felt by the subject, and also that the instructions aren't all that clear. For example one requires you close your eyes, look up, count to 30, and then stop the task while the police officer times you. I don't believe all people would count thirty seconds consistently, I certainly wouldn't be accurate in this. Nor would I likely be able to place one foot in front of another so stringently, or maybe stand on one foot under pressure.

Many of the people commenting on the video have expressed exactly what I feel, that even 100% sober I would fail this test.

So my question are:

1) What's the point of spending so much time going through this procedure if the main point of it is to establish probable cause, which can also be established with a 5 second breath test, which is also preliminary test to establish probable cause.

2) Isn't it unreasonable to expect normal people to pass these tests? Walking a straight line and counting the steps while remembering which foot to start from seems overwhelming to me, as does counting 30 seconds, and many of the other tests.

  • 1
    Remember, impaired driving isn't just about alcohol, you can get a DUI for smoking marijuana or other illicit substances.
    – Ron Beyer
    Commented Nov 1, 2018 at 17:41
  • @RonBeyer Yes, I'm sure there are many things which could impair someone's driving or ability to do the sobriety tests, I just mentioned alcohol in general. Also, I'm not sure if this is the correct site for this question, I tried to find SE site with more of a law enforcement subject, but this is the closest I could find.
    – Zebrafish
    Commented Nov 1, 2018 at 18:01

1 Answer 1


Florida law says that consent is statutorily deemed to have been given to "submit to an approved chemical test or physical test including, but not limited to, an infrared light test of his or her breath for the purpose of determining the alcoholic content of his or her blood". However, it is also required that

the person is lawfully arrested for any offense allegedly committed while the person was driving or was in actual physical control of a motor vehicle while under the influence of alcoholic beverages.

(that is, the person has to be arrested). Moreover,

The chemical or physical breath test must be incidental to a lawful arrest and administered at the request of a law enforcement officer who has reasonable cause to believe such person was driving or was in actual physical control of the motor vehicle within this state while under the influence of alcoholic beverages.

The breathalyzer test cannot be used in a fishing expedition: you need probable cause to legally administer it, and it is not voluntary.

Field sobriety tests can be administered when an officer has a reasonable suspicion of intoxication and thus have pulled you over (a "terry stop"), but the test is optional, that is, you can refuse to take that test. The results of the FST may provide the probable cause required for an arrest and a breathalyzer test. Mathis v. Coates, 24 So.3d 1284 points out that "Many factors contribute to a finding of probable cause for a DUI arrest" (and they discuss some). The test (and failing it) can create the required probable cause for arrest and subsequent breathalyzer test. As for why people consent to the FST in the first place, it is similar to people being talked into "consenting" to vehicle searches after being persuaded by the police to allow the search.

  • So - are you saying that it's not required, and probably a bad idea, to consent to a field sobriety test?
    – brhans
    Commented Nov 1, 2018 at 18:20
  • 1
    It is not required, and I don't know if there is any research establishing that it's a bad vs. good idea (i.e. probability of subsequent arrest). DUI attorneys say that it's a bad idea, but that have a particular perspective. I doubt there is any evidence that consenting to FST has a positive outcome for suspects.
    – user6726
    Commented Nov 1, 2018 at 18:27
  • This may be only applicable to Florida, and other states may have different laws. For example I was pulled over by Michigan State Patrol a number of years back and administered an FST (which I passed) and was also asked to take a breathalyzer (which I also passed). At no time was I ever arrested. There may have been additional circumstances which allowed them to administer the breathalyzer (I was seen leaving a bar and didn't use a turn signal to enter the roadway).
    – Ron Beyer
    Commented Nov 1, 2018 at 18:42
  • This seems very interesting, that in Florida a breathalyser test cannot be given unless a person is under arrest. However I find it a bit odd to refer to a breathalyser test as a fishing expedition. If a breathalyser is a fishing expedition then I'd be inclined to say the FST is one too, albeit a way less objective and accurate one. In that video it took 12 minutes to give the FST. Where I'm from in 12 minutes a police checkpoint can give a preliminary breath test to maybe 24 people. Likewise for single cases, instead of an FST you blow into a machine which takes no longer than 30 seconds.
    – Zebrafish
    Commented Nov 1, 2018 at 19:28

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .