You might wonder why the police do not take one of the most obvious steps they could to catch drunk drivers. If the police were to park outside a bar and test everyone getting into their vehicle, then they could catch anyone who is intoxicated and prevent them from harming themselves or others.
The reason the police do not do this is that it could be viewed as a breach of people’s Constitutional rights. It is not against the law to consume some alcohol before getting in your car and driving, unless you are subject to a zero alcohol limit, such as is the case for those under 21. Besides, not everyone who leaves a bar has consumed alcohol. For all the police know, someone who has been in a bar could have been drinking Pepsi or alcohol-free beer.
So, if the police sit there and breath test people coming out of the bar, it would signify they are making the assumption that just because someone has been in a bar means they are automatically going to break the law. In other words, they would be treating all the clientele of that bar as if they were criminals. Bar owners would likely also claim that the police are making it hard for them to earn an honest income, as the police presence would drive many customers away.
Reasonable suspicion
The law states that the police need reasonable suspicion that a driver has broken a law to pull them over. So, in the case of a driver, they’d need to see something such as the driver going through a red light, weaving all over the road or drinking beer out of a bottle as they drive along. They can’t see that if they intercept the person before they even reach their vehicle
Nevertheless, police officers sometimes do stop people without reasonable suspicion that they have broken a law. If this happens to you and they arrest you for drunk driving, proving the stop was illegal may be the grounds you need to fight the charges.