It's the prosecution's job to prove a radar reading is accurate — not the driver's job to prove it isn't. A 2007 Appellate Term case shows what happens when a trial court gets that backwards, and what's actually missing when a moving-radar case falls apart.
The Facts of the Case
Kahan was convicted of speeding in the Town of Deerpark, Orange County, based on a police officer's testimony that moving radar had recorded his speed at 51 mph in a 30 mph zone. Representing himself on appeal, Kahan argued the trial court had erred in relying on that testimony.
The trial court's own written return revealed the problem: it stated that Kahan "has no proof now or during trial in regards to his claim that radar is inaccurate if patrol vehicle is in motion." In other words, the court had treated the absence of evidence disproving the radar's accuracy as a reason to convict — rather than asking whether the prosecution had proven the radar was accurate in the first place.
The Question on Appeal
Had the trial court improperly shifted the burden of proof onto the defendant, and was the officer's bare testimony about the radar reading legally sufficient on its own?
Case on Point
The Appellate Term held that the trial court had improperly shifted the burden of proof from the prosecution to the defendant regarding the accuracy of the particular radar unit involved. It further held that the officer's testimony that moving radar disclosed a speed of 51 mph in a 30 mph zone was legally insufficient to sustain the conviction, reversing the judgment, remitting the fine, and dismissing the simplified traffic information.
People v. Kahan, 16 Misc.3d 37 (2007)
What the Record Was Actually Missing
The court measured the record against the moving-radar standard the Court of Appeals set out in People v. Knight: because moving radar has to measure the patrol car's own speed in addition to the target vehicle's, the prosecution carries a heavier burden than it would with stationary radar. That means showing the unit was in proper working condition and operated by someone qualified, that the officer independently verified the patrol vehicle's own speed, and that the radar was used somewhere posing minimal risk of misidentification or signal distortion — heavy traffic, large trucks, or roadside objects like billboards.
None of that was in the record here. There was no testimony that the officer had verified the patrol car's speed against its own speedometer, and nothing addressing the conditions where the radar was used. Viewing the evidence in the light most favorable to the prosecution, the court still found it fell short of proving guilt beyond a reasonable doubt.
Key Takeaway: A bare radar number, without testimony addressing the Knight factors, isn't enough for moving radar — and a defendant is never required to disprove the radar's accuracy. If the prosecution's evidence doesn't affirmatively establish the unit's accuracy, the case fails regardless of what the defense does or doesn't produce.
What This Means for a Defense
Kahan offers a clear checklist for evaluating any moving-radar case:
- Watch for burden-shifting language. If a court's reasoning turns on what the defendant failed to prove, rather than what the prosecution affirmatively established, that's a legal error worth raising on appeal.
- Check for patrol-vehicle verification. The prosecution has to show the officer independently confirmed their own vehicle's speed — a bare radar reading of the target vehicle isn't enough for moving radar.
- Check for testimony about the conditions. Heavy traffic, large trucks, and roadside objects like billboards are the specific distortion risks courts look for testimony to rule out.
Told You Had to Prove the Radar Was Wrong?
That's backwards. The prosecution has to prove the radar was accurate — not the other way around. Find out whether your case actually meets that burden.
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