How Do Police Determine Whether a Driver Is too Impaired to Drive?

It is the responsibility of every driver to avoid getting on the road while impaired. However, it is also useful to understand the laws surrounding DUIs. A big question many people have is how officers actually determine whether someone is too impaired to drive. This is actually a more complicated matter than you might think. This simple guide will explain the answer to this question.

Determining Impairment

Many people do not realize that there are actually two ways someone can be considered too drunk to drive. There is an objective limit and a subjective limit. It is illegal for adults to drive with a blood alcohol content above 0.08%. This is objective, but it is also impossible to determine without taking a sobriety test, which is not legally required in nearly all cases. That is why there is a second requirement, which is simply whether someone is “too impaired to drive safely.”

As you can tell, this is a subjective matter. It is up to the arresting officer to determine whether or not someone is too impaired to drive safely. This matter will mostly be determined by the driving behavior of the individual, such as:

  • Swerving or drifting in the lane
  • Colliding with objects or vehicles
  • Driving too fast or slow
  • Driving recklessly

These are all reasons why someone might be pulled over, and if the officer can confirm that these driving behaviors are due to drunkenness, then it is safe to assume the individual is too impaired to drive safely. Keep in mind that more things than just alcohol can impair your driving ability, from emotional trauma to other mind-altering substances.

Probable Cause

Officers need something called probable cause to actually arrest someone for impaired driving. Probable cause is essentially just tangible proof of impairment. In the case of drunkenness, probable cause may take the form of empty alcohol containers, drunken behavior, slurred speech, the smell of alcohol, or a failed sobriety test.

If an officer arrests you for a DUI without probable cause, then the case will almost certainly be thrown out. Even if real proof is discovered after the arrest, it is illegal for an officer to make that initial arrest without proof. If you think you have been arrested without probable cause, you should immediately hire a DUI attorney so you can have your case properly dismissed. It is a good idea to hire an attorney no matter what if you have been arrested for a DUI.