Field Sobriety Tests in New Jersey

What Field Sobriety Tests Are

When an officer suspects impairment during a New Jersey traffic stop, they often ask the driver to step out and perform a series of roadside tasks designed to gauge balance, coordination, and the ability to follow instructions. These are field sobriety tests, and the officer's observations during them frequently become a key part of the state's case in a DWI prosecution.

What many drivers don't realize is how much room for error these tests carry — and that, unlike the breath test after arrest, you are not legally required to perform them.

The Three Standardized Tests (SFSTs)

Three tests are recognized as "standardized" under federal NHTSA guidelines, meaning they're supposed to be administered and scored in a specific, consistent way:

1. Horizontal Gaze Nystagmus (HGN)

The officer asks you to follow a pen or finger with your eyes while watching for involuntary jerking (nystagmus). The problem: nystagmus has many causes unrelated to alcohol — including certain medications, neurological conditions, fatigue, and even the flashing lights of the patrol car — and the test is easy to administer incorrectly.

2. Walk-and-Turn

You're asked to take nine heel-to-toe steps along a line, turn, and return while the officer counts "clues" such as stepping off the line or starting too soon. Balance problems, injuries, age, weight, footwear, and an uneven or sloped roadside can all produce clues in a perfectly sober person.

3. One-Leg Stand

You're told to stand on one foot and count aloud while the officer watches for swaying, hopping, or putting your foot down. As with the walk-and-turn, physical condition and roadside conditions heavily influence the result.

Why These Tests Are Often Unreliable

Even administered perfectly, the standardized tests are only partial indicators of impairment — and conditions on a real roadside are rarely perfect. Factors that can cause a sober person to "fail" include:

• Medical and physical issues — inner-ear problems, back, knee, or leg injuries, neurological conditions, and obesity.
• Age and nerves — older drivers and anyone anxious about a police encounter struggle with balance tasks.
• Environment — uneven pavement, gravel, slopes, poor lighting, wind, rain, and passing traffic.
• Footwear and clothing — heels, boots, or restrictive clothing affect balance.
• Administration errors — unclear instructions, improper demonstration, or scoring that doesn't follow the standardized protocol.

These tests matter beyond just supporting a breath test result — they're also the main evidence New Jersey relies on when there's no BAC reading over the legal limit at all. See our page on getting a DWI with a BAC under 0.08% in New Jersey for how that impairment-based charge works.

Are Field Sobriety Tests Mandatory in New Jersey?

No. Field sobriety tests are voluntary. This is an important distinction. New Jersey's implied consent law applies to the breath test administered at the station after a lawful arrest — refusing that test carries its own penalties (see our breath test refusal guide). The roadside balance and coordination tests are different: declining them does not trigger the same automatic refusal penalty. That said, every stop is fact-specific, and how an officer responds varies — see our page on whether you can refuse field sobriety tests in New Jersey for a full walkthrough of what actually happens if you decline and how to weigh that decision at the roadside. This is a separate question from whether the officer had to warn you about your rights before asking — see our page on Miranda rights during a DWI stop in New Jersey for how that timing actually works.

How Field Sobriety Results Can Be Challenged

Because these tests are subjective and depend entirely on proper administration, their results are among the most frequently challenged pieces of evidence in a DWI case. A close review often focuses on:

• Whether the officer followed the standardized NHTSA procedures for each test.
• The physical condition of the driver and any medical explanations for the observations.
• The roadside conditions — surface, lighting, weather, and traffic.
• What dashcam or bodycam footage actually shows versus what the report claims — see our page on video evidence in DWI cases for how that comparison typically gets made.

If you already performed these tests, that does not mean your case is decided. The same evidence the state relies on can cut the other way once it's examined carefully alongside the stakes you're facing.

These tests aren't limited to standard traffic stops, either. Officers sometimes administer them at the scene of a parked vehicle — someone found asleep behind the wheel, for example — where the results become part of a broader question about whether the vehicle was even being "operated." See our page on DWI in a parked car in New Jersey for how that specific scenario is evaluated.