A “per se” DUI charge is based on a driver having a certain amount of drugs or alcohol in his or her blood. All states have laws that prohibit driving with a blood alcohol concentration (BAC) of .08% or more. (Get an estimate of how many drinks it takes.) And a number of states also have laws making it illegal to operate a vehicle with a certain amount of drugs in your system.
Though it’s also a crime to drive while impaired by drugs or alcohol, per se DUI laws don’t require proof that the driver was actually affected by the drugs or alcohol ingested. To get a per se DUI conviction, the prosecution just needs to show the motorist was driving with the prohibited concentration of drugs or alcohol in his or her body.
Implied consent laws generally require all drivers lawfully arrested for driving under the influence to take BAC test (typically, a blood or breath test). So, in most DUI cases, the prosecution will have test results showing the amount of drugs or alcohol in the driver’s system.
Sometimes BAC test results make it easy for the prosecution to prove the charge. But in other cases, defenses attorneys are able to poke holes in the prosecution’s evidence by finding problems with the testing equipment or procedures. (For instance, read about the “rising-blood-alcohol defense.”) Every case is different. So, the best way to find out where you stand is to talk to an experienced DUI attorney.(Read about the DUI laws in your state and get other DUI questions answered.)