Police are often trained to take cautious procedures when handling drivers who are pulled over under the suspicion of driving under the influence of drugs or alcohol. When judging their inebriation levels, they may ask the driver to take a breathalyzer test. This test evaluates the blood alcohol concentration (BAC) levels in their breath – a BAC of 0.08% or above is considered against the law and may lead to a license suspension, fines or incarceration.
Oftentimes, before asking for a breath test, officers will likely ask the suspect to act out several standardized field sobriety tests (SFST). An SFST is a sort of technique officers use to collect evidence on a suspected drunk driver. There are typically three kinds of SFST:
Horizontal gaze nystagmus test
A horizontal gaze nystagmus test has the suspect follow a single point, a finger, pen or light, with their eyes without moving their head. Police typically look for any anomalies that may indicate the suspect is drunk. For example, if the suspect has a delay when focusing on the point or if their eyes flicker to attention something else.
Police may ask the suspect to perform a walk-and-turn test. This test has the suspect walk in a straight line, stop and walk back to where they started. If the suspect drifts off the line, falls over or can’t finish the test, then they may fail the test.
One-legged stand test
The one-legged stand test is as straightforward as the name suggests; the suspect balances on one leg. The officer is likely looking to see if the suspect can perform the simple action and keep balance. Someone who is under the influence may lose balance or fail to do the test altogether.
Non-standardized field sobriety test
Alternatively, police may use a series of non-standardized field sobriety tests. These tests may involve the suspect listing off the alphabet backward while doing jumping jacks or having the suspect stretch out their arms and touch their nose.
These tests often seem like monkey tricks used to humiliate suspects – and that’s not far off. There’s often no science involved in SFSTs and many conclusions are invalid. While drivers aren’t required to do SFSTs if requested, people may still need to know their legal options when dealing with a DUI charge.