If the police give someone a breath test, they can measure the amount of alcohol in their system. This can also be done through urine tests or blood tests, and all of this is considered to be very reliable. It can tell if someone’s blood alcohol concentration was over the legal limit of 0.08%.
However, when a police officer stops a vehicle, he or she does not know if that driver is impaired and has no access to the Breathalyzer at the station. There are portable breath tests, but these often cannot be used in legal proceedings, so the police need some other way to determine if someone may be impaired. They often do this with field sobriety tests.
There are three types of tests
The three main types of field sobriety tests are the one-leg stand, the walk and turn and the horizontal gaze nystagmus. These may be used individually or all together. You do sometimes hear myths about police officers asking people to recite the alphabet backward or something of this nature, these are not standard tests and are actually not used.
Unfortunately, these tests that are used are not as reliable as people sometimes assume. Some studies have found error rates of 47%. The best results have been provided when people are subjected to all three tests in a row, but even then there is a significant error rate.
For instance, you could simply be tired after a long day at work and stumble while doing the walk and turn test. You could be suffering from some sort of illness or disease that impacts your balance, and that could make the one-leg stand difficult.
So it is true that these tests can help to determine if someone is intoxicated, in the sense that someone who has no outside factors should probably pass them. But the reality of the situation is that most people have other factors that are going to influence how they do on the test, especially when they’re being subjected to that test suddenly and on the side of a random road.
What options do you have?
You can see that this is not a reliable system, but it still does lead to arrests, which is why you need to know about all of your defense options.