In New Jersey, a person is presumed to have committed DUI/DWI when they have a blood alcohol concentration of 0.08 percent or more while operating a motor vehicle. Drivers under the age of 21 in New Jersey may not have any detectable alcohol in their system. In addition, drivers can be charged with DUI/DWI if they have any detectable narcotic, hallucinogenic, or habit-forming drugs in their system. Of course, a driver whose BAC is below the legal limit may still be arrested for DUI/DWI if they have consumed alcohol that has negatively impaired their ability to safely operate a motor vehicle.