The mistake that sends people to Google from the shoulder of the FDR Drive near 96th Street on New Year's Eve is thinking, "I stumbled on the roadside tests, so the case is over." It is not.

In New York, those roadside exercises are usually the three standardized field sobriety tests: Horizontal Gaze Nystagmus, Walk-and-Turn, and One-Leg Stand. They are supposed to be given in a very specific way under NHTSA standards. If the officer rushed the instructions, demonstrated them poorly, had you do them on a sloped shoulder, in bad lighting, in winter boots, or while traffic and emergency lights were flashing around you, that matters.

So do medical issues. Knee, ankle, back, hip, or foot injuries, vertigo, inner-ear problems, neuropathy, diabetes, some neurological conditions, eye issues, age, weight, fatigue, and limited English can all make these tests look worse than they are. In Manhattan holiday enforcement, officers are moving fast. Fast is not always clean.

What matters next is the difference between roadside tests and the official evidence. A field sobriety test is not the same as a chemical breath test. The prosecution still has to prove impairment under New York Vehicle and Traffic Law § 1192. If you have a prior DWI-related conviction within 10 years, a new DWI can be charged as a felony under § 1193, which is why the details of the stop become much more important this time.

The useful approach is to pin down facts while they are fresh:

• Exact location of the stop or checkpoint
• Shoes, weather, road surface, injuries, and medical conditions
• Whether instructions were clear and whether the officer demonstrated each test
• Whether body-worn camera, dash camera, or checkpoint video likely exists
• Whether there was a later chemical test or a refusal issue with the New York State DMV

In Manhattan, the case usually lands in New York County Criminal Court, but the roadside test problems can be some of the strongest issues in the file.