When you’re pulled over for a traffic violation and the officer thinks you may have been drinking, there are many different tools they use to determine whether you’re drunk. They may visually inspect the car for bottles or signs of drinking, they might notice whether you smell like alcohol, and they may take you through a series of approved “field tests” to determine whether you can complete basic tasks a sober person is expected to be capable of performing. However, no law enforcement tool is as certain as a breathalyzer or blood test – in theory.

Both breath tests and blood tests are supposed to be precise, accurate measures that definitely show the amount of alcohol in your bloodstream, which is the legal metric for whether you are too drunk to drive. But even though these tests are far more scientific than “field tests” they’re far from perfect.

If you have a skilled DUI lawyer at your side, you have a chance to fight back against evidence gathered by these tests. Here are things you should know about blood alcohol tests of any kind:

  • If you are arrested for DUI you are required to submit to a test. If you refuse you will not be forced, but refusal is not wise. It results in immediate revocation of your driver’s license. It will also be seen as admission of guilt and the prosecution will use this fact against you.
  • Breath tests are not flawless. There is evidence that certain conditions can throw off the accuracy of breath tests and even lead to a false positive. Your lawyer can help you discover whether there are circumstances that call the validity of the results into question.
  • Testing equipment must be properly calibrated. Breathalyzers need to be calibrated on a regular schedule and their data carefully downloaded. All the data for all the tests a machine has done must be available for your legal team to review, to verify whether it is performing reliably.
  • Procedural irregularities can mean evidence is thrown out. Officers are legally required to follow correct procedures during and after the arrest. If these procedures are not followed, the evidence gathered may be suppressed from the court proceedings.

Not every case will have faulty, irregular, or inadmissible blood test evidence. But a good DUI defense lawyer will thoroughly pursue every avenue. In some cases, the District Attorney’s office will drop thre case or offer a bargain simply because a defendant has hired a skilled DUI attorney.