Most of the time, officers don’t know that a person is actually drunk when they pull that person over. You can bet, however, that they’re suspicious. It’s not just the commission of a traffic violation itself that gives them suspicion. It could very well be a number of things.
What do officers look for when spotting a suspected drunk driver?
How well can they keep their balance?
Because people who are under the influence have trouble with vision and balance, they often have trouble driving in a straight line. They may weave through traffic, not stay in their own lane, drift, straddle one side of a lane, swerve, and/or make wide turns. The California Court of Appeals has held that “pronounced weaving within a lane provides an officer with reasonable cause to stop a vehicle on suspicion of driving under the influence where such weaving continues for a substantial distance.”
Do they have good spatial judgement?
Drivers who are under the influence also often have trouble gauging speed and distances. As a result, many drunk drivers have trouble stopping their vehicles as a sober person would. This includes stopping their vehicle too far from a curb or a stop sign, as well as stopping their vehicle suddenly.
Do they have control of their motor skills?
Similarly, drunk drivers may also have trouble accelerating. Often, they will accelerate abruptly rather than gradually. Additionally, they might have trouble maintaining a consistent speed. It would be unreasonable to expect a person to maintain the speed perfectly. However, the speed fluctuations of drunk drivers are much more drastic than sober drivers.
What I’ve mentioned are what officers look for, but what about what they listen for? I’m not talking about the sound of drunk drivers. I’m talking about anonymous tips from callers who may suspect that a person is driving drunk. Can an officer use an anonymous tip to help him or her “spot” a drunk driver?
Navarette v. California
In the case of Navarette v. California, the United States Supreme Court held that anonymous tips can give law enforcement authority to pull someone over on suspicion of driving under the influence. This is true even though it is impossible to verify the reliability of the tip and the officer has not witnessed any driving that would indicate intoxication.
These are some things that give officers the authority to pull someone over with only the suspicion that they are driving under the influence. However, they are not enough to give the officer the probable cause for an arrest for driving under the influence.
Once pulled over for the reasons mentioned above, the officer can make their own observations to substantiate their suspicions. These are the pieces of information that have become common in DUI police reports. These include the smell of alcohol, the slurring of words, and the bloodshot and watery eyes of the driver. After that, few things can help produce the probable cause needed to make the DUI arrest. These include the driver agreeing to and failing field sobriety tests. The driver could also produce a breathalyzer above 0.08 blood alcohol content.