Field Sobriety Tests

How It’s Administered

The officer holds a stimulus — usually a pen or fingertip — about 12 to 15 inches from your face, slightly above eye level, and moves it slowly side to side while watching your eyes. You are told to follow the stimulus with your eyes only, without moving your head.

What Officers Score as Clues

• Lack of smooth pursuit — the eye jerks as it tracks the stimulus instead of following it smoothly
• Distinct and sustained nystagmus at maximum deviation — the eye jerks noticeably when held at the far corner for at least four seconds
• Onset of nystagmus prior to 45 degrees — jerking begins before the eye reaches a 45-degree angle

Decision point: 4+ clues suggests BAC ≥ 0.08%

Where It Falls Apart

• Dozens of medical conditions cause nystagmus with zero alcohol: inner-ear problems, brain injury, hypertension, caffeine, nicotine, and certain prescription medications
• Flashing police lights or passing traffic in your field of view can trigger optokinetic nystagmus — NHTSA's own manual says the test should face you away from them
• Timing errors are common: each pass has a prescribed speed (roughly two seconds out, two seconds back) and the officer must hold the stimulus at maximum deviation for a minimum of four seconds
• Holding the stimulus too close, too high, or moving it too fast invalidates the clue

How It’s Administered

A divided-attention test in two stages. First, the instruction stage: you stand heel-to-toe with arms at your sides while the officer explains and demonstrates. Then the walking stage: nine heel-to-toe steps down a real or imaginary line, a prescribed series of small pivot steps to turn, and nine heel-to-toe steps back — counting out loud, watching your feet, arms at your sides.

What Officers Score as Clues

• Cannot keep balance during instructions
• Starts before instructions are finished
• Stops while walking
• Misses heel-to-toe (more than half an inch)
• Steps off the line
• Uses arms for balance (raises more than six inches)
• Makes an improper turn
• Takes the wrong number of steps

Decision point: 2+ clues suggests BAC ≥ 0.08%

Where It Falls Apart

• NHTSA's validation studies excluded people over 65, those more than 50 pounds overweight, and those with back, leg, or inner-ear problems — yet officers give the test to everyone
• The standardized conditions require a hard, dry, level, non-slippery surface and a visible line — a sloped freeway shoulder at 1 a.m. is none of those things
• Heels higher than two inches: NHTSA says you should be offered the chance to remove them. Many officers never do
• An officer who demonstrates the turn incorrectly, or never says 'keep your arms at your sides,' has scored you on instructions you were never given

How It’s Administered

You stand with feet together and arms at your sides, then raise one foot approximately six inches off the ground, toe pointed, both legs straight, and count out loud — 'one thousand one, one thousand two…' — while looking at your raised foot. The officer times the test for 30 seconds.

What Officers Score as Clues

• Sways while balancing
• Uses arms for balance (raises more than six inches)
• Hops to maintain balance
• Puts the raised foot down before time expires

Decision point: 2+ clues suggests BAC ≥ 0.08%

Where It Falls Apart

• Standing on one leg for 30 seconds is hard for many sober people — the same age, weight, and injury exclusions from the WAT studies apply here and are routinely ignored
• If the officer fails to time the full 30 seconds, the scoring is invalid — most impairment-related foot-downs occur after the 25-second mark
• 'Sways while balancing' has no objective measurement; it is whatever the officer says it is
• Gravel, rain, wind, cold, and darkness all degrade balance and were never part of the validation conditions