A New Jersey police officer pulls you over and has you blow into a device called a breathalyzer. According to the officer, the breathalyzer has registered a blood alcohol level that is above the legal limit. You might think the officer has irrefutable evidence that you were driving under the influence, but this is not necessarily the case.
A breathalyzer does not always produce accurate results. As WebMD explains, there are some factors that can throw off breathalyzer readings. As a result, a court might decide that the breathalyzer results are not admissible as evidence.
Substances you ingest
If you only had a drink or two that did not raise your BAC level above the legal limit, the alcohol could still register a false positive because some of it may remain in your mouth 15 minutes prior to a breath test. Some substances like mouthwash and breath fresheners may also inflate BAC levels since they contain some alcohol. Additionally, breathalyzers may produce unreliable results if you smoke.
Problems with the breathalyzer
Like any machine, a breathalyzer must be in working order to produce correct results. An unreliable breathalyzer may require recalibration, or it may have low or bad batteries. Some breathalyzers also operate on computer software. In the event a breathalyzer has not received a software update, it might not function as intended. In general, a failure to maintain the breathalyzer may result in problems with its accuracy.
Sometimes a police officer mishandles the breathalyzer. A possible defense against a high BAC result is that the officer did not receive the training needed to use a breathalyzer or was otherwise not qualified to operate the device. These or other factors may be decisive in combating DUI/DWI charges against you.