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How can the police tell a driver is impaired?

On Behalf of | Mar 26, 2023 | DUI |

The police need reasonable suspicion to initiate a driving under the influence (DUI) of alcohol or other drugs stop. Stopping without showing signs of being impaired or simply because a driver is coming from the side of a bar may constitute an illegal stop. 

DUI is dangerous and carries significant consequences. Thus, the police pay attention before stopping a driver and obtaining an alcohol concentration test. Here is how a police officer can tell a driver is impaired:


A drunk driver may have poor coordination. It may be challenging for them to maintain the vehicle in a straight line. Thus, they will swerve, which is one of the telltale signs of drunk driving.

Aggressive behaviors

Alcohol and other drugs can encourage a driver to have aggressive behaviors. This is due to the false sense of invincibility and increased confidence associated with intoxication. Such a driver may speed, tailgate, change lanes unsafely, run a stop sign or red light and fail to yield to other road users.

Quick acceleration and deceleration

Impaired judgment is one of the consequences of alcohol. Thus, a drunk driver may not make the best decisions concerning speed. They may feel like they are driving slowly and suddenly accelerate. Then, after some time, they may think the speed is high and, in turn, slow. This sudden acceleration and deceleration behavior can inform the police that a driver may be drunk.


When someone is drunk, they can be suspicious. They may believe everything they do tells people they are drunk. Therefore, they can overcompensate. They may brake early or drive extremely slowly. Unfortunately, the harder they try to hide their impairment, the easier the police can spot them.

Sometimes, however, the police jump to the wrong conclusion. If the authorities charge you with a DUI, it can help to obtain more information about the defenses you can use based on the specifics of your situation.