When they have pulled over a driver on suspicion of drunk driving, police have several ways of collecting evidence to show that a driver was intoxicated. They write up a report in which they document their observations, including the words and actions of the driver, whether they smelled alcohol on the driver’s breath, and how the driver performed simple tasks, such as walking a straight line. But some of the most effective evidence they gather is the result of a blood alcohol concentration, or BAC, test. An adult whose BAC is 0.08% or higher is legally too drunk to drive.

The most common way of administering a BAC test in New York and throughout the nation is through a chemical breath analysis device, commonly known as a Breathalyzer. But these devices are not always reliable.

In fact, the New York Times recently conducted a multi-state investigation that found widespread problems with Breathalyzer devices, including operator errors, faulty calibration, software glitches and more. In one case, police used a breath testing device that had rodents nesting inside it.

One of the most powerful strategies in DUI defense is to question the reliability of the BAC test. If a defendant can show that the Breathalyzer device was faulty, or that the results were unreliable for some other reason, the court may throw out the evidence of the test. If a court does this, it knocks out some of the most powerful evidence the prosecution has against the defendant. Prosecutors will still have the rest of the evidence from the police report, but without the BAC test results, they will have a harder time proving their case.