Chemical testing is not an exact science, and errors are often made. It takes anywhere from 45 minutes to several hours for alcohol to be absorbed into the bloodstream. From the time you are initially stopped until you submit to an official blood alcohol test at the police station, your blood alcohol level may go up substantially. If you were stopped shortly after consuming alcohol, your body is still absorbing the alcohol. Rising blood alcohol can be the difference in whether you were driving under the influence. An experienced California DUI attorney may use the defense that the driver's blood alcohol level did not meet the legal limit of impairment while you were operating a motor vehicle, only later when you were tested. A toxicology expert can provide supporting expert testimony based on the number of drinks you consumed, stating that you weren't over the limit at the time of your arrest and your impairment didn't occur until you were no longer operating a vehicle.
Explanation for poor driving
Yes, you were weaving in and out of your lane. You were talking on a cell phone and trying to write down an address when you were supposed to be paying attention to the road. Drivers have many distractions that can cause them to drive with less focus on the road than they should have. These factors can explain your driving behavior rather than having had too much to drink.
Improper DUI checkpoint
The California Highway Patrol and local police departments hold sobriety checkpoints to reduce the number of drunk drivers on the highways. But police must follow certain guidelines to comply with the law and avoid constitutional prohibitions against unreasonable search and seizure. Police must announce in advance the location of the sobriety checkpoint, and choose a time and place where alcohol related arrests are common. They must follow a formula such as stopping every car, or every fourth car. They must keep the length of detention of each motorist to a minimum. But police do not always follow the guidelines, and a skilled DUI lawyer may be able to challenge a DUI driver's arrest at a sobriety checkpoint.
No driving defense
If the police found you when you were in a parked car and no one saw you operating a vehicle, the police will have only circumstantial evidence that you were driving under the influence. If the prosecutor can't prove that you were driving, then you can't be convicted of driving under the influence. But the defense strategy may open you to other charges, such as possession of an open container of alcohol or public drunkenness.
A breath test machine may provide a false reading. The police department must maintain the alcohol testing equipment. But many cash-strapped law enforcement agencies neglect to recalibrate the equipment regularly. They're required to keep maintenance records on the testing equipment. An aggressive DUI defense lawyer will demand maintenance records on the breathalyzer machine during the discovery process as one of the ways to beat a DUI.