Most drivers have heard of the so-called legal limit for alcohol, but many do not fully understand what this means. In this blog post, we will look at some of the details.
Blood alcohol concentration
The “legal limit” refers to a measurement of the percentage of alcohol in a driver’s bloodstream. This type of measurement is known as blood alcohol concentration, or BAC.
Police typically measure BAC by using a chemical breath test at the roadside, but in some situations they can also take drivers to a facility for a blood or urine test. These types of tests are considered more accurate than breath tests.
If the test finds a driver’s BAC to be 0.08% (0.08 grams per 100 mL of blood) or higher, Virginia law considers them to be intoxicated “per se,” meaning that the driver has broken the law. This is what most people are referring to when they talk about the “legal limit.”
What if the BAC is below 0.08%?
Talking about 0.08% as the legal limit is somewhat misleading. For one thing, not all drivers have the same legal limit. A driver under age 21 is considered intoxicated per se if their BAC is a mere 0.02%.
What’s more, the figures we have discussed so far apply only to alcohol. Virginia has other limits for other intoxicants. A driver can be found to be intoxicated per se if they have as little as 0.1 milligrams of methamphetamine per liter of blood. The acceptable percentages are even smaller for drugs such as cocaine.
It’s also important to note that the police do not need to have the results of a BAC test to arrest a driver if they have evidence the person was too intoxicated to drive safely. Even if they don’t have access to breath, blood or urine tests, they can conduct a roadside sobriety test, in which they ask a driver to perform simple tasks designed to show their coordination. They can also take note of the smell of alcohol on a driver’s breath, or whether the driver was slurring words.
Prosecutors can rely on this evidence to prosecute DWI charges against a driver, and they can win a conviction.