In order to arrest someone on suspicion of drunk driving, police must have probable cause. This means that they can't just have a hunch that you are intoxicated. They must gather sufficient evidence to arrest you.
Since roadside breath tests are highly unreliable, authorities needed to create some other method to determine impairment. This is when the National Highway Traffic Safety Administration conducted some research and came up with a three-part test back in the 1980s. Police officers still use those tests today.
The Standard Field Sobriety Tests
The tests approved by the NHTSA involve the following three tests:
- The walk and turn test requires you to walk a certain number of steps heel to toe in one direction and then turn around and do the same in the other direction. The officer watches to determine whether you have an issue balancing, following directions or completing the test without stopping, among other things.
- The horizontal gaze nystagmus test measures the involuntary jerking of your eyes when following an object. Everyone's eyes begin to jerk at a certain point, but when impaired, that movement supposedly begins within a smaller range.
- The one leg stand test requires you to stand on one leg while counting out a certain number of seconds. If you lose your balance, use your arms to stabilize yourself, put your foot down or hop to keep your balance, it supposedly indicates impairment.
It doesn't take long to realize that so much could go wrong with these tests. First, the officer's subjectivity plays a substantial role in whether you "pass" or "fail" the tests. After all, the officer already suspects you of being intoxicated; how much does he or she really give you the benefit of the doubt? Moreover, any number of physical illnesses or injuries can impair your ability to complete the tests.
Do you have to take the tests?
Legally, you do not have to take these tests. When you received your Massachusetts driver's license, you did agree to submit to testing to determine your blood alcohol content, but taking these tests is not part of that deal. You could still face a DUI charge, but at least the officer will not have the results of these tests to establish probable cause or use against you in court. However, a prosecutor could tell the court that you refused to take the tests, which may not look good for you.
Deciding whether to submit to these tests is a personal decision. Whether you do, if you ended up in police custody, you have the right to challenge the charges, along with any testing done that allegedly indicates you were impaired at the time.