Blood tests have traditionally proven to be more accurate than breath tests when police are checking to see if a driver is over the legal limit. That limit has been set for most drivers at 0.08—it’s only different in some cases for commercial drivers and underage drivers. Though blood tests are better, the breath test is simple and effective, and many mobile devices can be used by police on the scene to decide if a DUI is warranted.
However, it is very important to note that a breathalyzer must be calibrated correctly to provide accurate results. Even the slightest degree off from perfect can make a huge difference. If a driver comes in at 0.07, he or she is allowed to go without issue, but, just .02 higher, at 0.09, that driver will be given a DUI.
The officers are supposed to do regular maintenance on their breath test devices, and they are supposed to calibrate them on a predetermined schedule. This is different for the various makes and models out there, but it is crucial that the officers follow that schedule or they can’t know that the unit is giving them a real reading. While it may be close, as is noted above, that it is not good enough.
If you have been given a DUI after a breath test, you have the right to challenge the test if you believe you should do so. One of the big reasons people are put in these challenges in Maryland is because they think that the breathalyzers were neglected and not calibrated when they should have been, leading to inaccurate readings and fraudulent chargers.