Drunk driving is a societal problem that everyone agrees needs addressing. To combat the matter, police officers have the right to conduct sobriety exams on motorists they suspect are under the influence.
Unfortunately, these intoxication measures are often unscientific. The horizontal gaze nystagmus test has various flaws. Shining a flashlight at someone, telling that person to follow your finger or a pen and looking for eye twitches will never definitively prove drunkenness. The following reasons explain why.
Problem #1: Physical issues can cause failure
Blood toxicity is not the only factor that can lead to someone bombing this exam. Various health conditions, such as infections, may trigger similar eye movements. Even eyestrain from long road trips may be a culprit.
Problem #2: Observation does not constitute proof
Everyone has biases that affect the way they see the world. Representatives of the law are not immune from this psychological dimension of humanity. One may start a test assuming the subject is guilty. Many cognitive biases could cause an officer to see someone as drunk when that is untrue.
Problem #3: Only blood tests determine the level of intoxication
Even in the case of failure, it may only mean that person has alcohol in their system. The driver could still be under the legal limit. Under such circumstances, getting behind the wheel is entirely acceptable.
The horizontal gaze nystagmus test is still a popular technique among law enforcement. They continue using it even though there are severe questions of reliability. Failure does not necessarily mean someone is breaking the law.
