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Field sobriety test vs. breath test: Is there a difference?

On Behalf of | Jun 23, 2023 | DWI Defense |

Public roads and highways are teeming with all sorts of fatal threats. But there is a unique fear that comes with a New Jersey police officer asking you to pull you over for driving while intoxicated (DWI) suspicion.

The state’s police officer can submit you to either a standardized field sobriety test (“SFST”) or a breath test (breathalyzer). Then, state prosecutors may use these tests as evidence against you, even if specific calibration and interpretation flaws reduce their validity.

As similar as they sound, these tests have key differences that can significantly impact your defense strategy in court. 

Fundamental differences

Under New Jersey law, an individual guilty of a DWI offense has varying degrees of punishment depending on the circumstances of their case. The penalties include hefty fines, prison time, community service, completion of a rehabilitation program and license suspension.

  • Unlike a field sobriety test, a breath test is compulsory: Any driver operating a vehicle on state roads and holding a state-issued driver’s license gives an “implicit consent” that they’ve agreed to submit themselves to a breath test. Conversely, a field sobriety test, commonly composed of the nystagmus, one-leg and walk-and-turn tests, is optional. However, not all police officers may present it that way, which usually compels drivers to subject themselves to the test.
  • The breath test has a scientific basis, while a field sobriety test is based on the police officer’s interpretation of standardized indicators: A breath test uses a Blood Alcohol Content (BAC) measurement, which should not exceed .08%. The legal limit may vary for minors. The state has zero tolerance for underage DWI, which means that a percentage lesser than .08% may be enough to trigger an arrest. Meanwhile, a field sobriety test has guidelines that an arresting officer must follow.
  • Both tests have distinct flaws: To invalidate a breath test, you may point out that the device is inadequately calibrated, cleaned, maintained and administered. You may also raise your concern about “false positives” due to a medical condition, or consumption of specific food, beverage or breath mints. Oppositely, the invalidation of a field sobriety test may be in insufficient explanation about the test mechanics, misinterpretation of performance or a medical condition affecting your eye movement, balance and coordination.

Although a police officer cannot physically force you to take a breath test, any form of refusal, like fake blowing or outright defiance, may subject you to an implicit consent law violation.

A sober perspective

Despite their fundamental differences, both tests aim to ensure that law enforcement keeps the roads safe for you and other drivers. It will help to discuss your options with a legal team and reach a sober decision.