Right for the Wrong Reason

By John Carr, NMA Massachusetts Activist

“It’s the ship that made the Kessel Run in less than twelve parsecs.” — Han Solo
(Nerd rage) — Astronomers everywhere


Last year an Ohio appeals court threw out evidence from a laser gun. Police were using an LTI UltraLyte but there was no evidence that the UltraLyte was reliable. Previous cases had only considered the LTI 20-20.

This year a federal appeals court threw out a police officer’s visual speed estimate when he couldn’t explain the math behind it.

Both courts reached the right result for the wrong reasons.

What’s in a name?

The Ohio court assumed that a finding that one device was accurate also validated other devices with the same name. The model name of a product is a marketing decision. The accuracy of a laser is determined by what’s inside the box. Upgrading from firmware revision 31 to 32 can be more important than changing the label from”Marksman” to “UltraLyte.” Conversely, the label can change while the guts of the unit remain the same.

A lawyer got lasers temporarily banned from New Jersey when he clocked the courtroom wall moving at high speed. New LTI lasers don’t make that error. They refuse to display speed for targets closer than 50 feet, like courtroom walls. Beyond 50 feet they are as accurate or inaccurate as ever. They look more accurate in a courtroom. All this is due to an otherwise-invisible change to a few lines of a computer program.

The Ohio court left open the possibility that admissibility could be based on finer distinctions than model name. Appeals courts are limited to considering evidence presented to the trial judge. The record didn’t even spell the name correctly.

If the goal were accuracy in courtrooms judges would require police to provide the model number, hardware revision, firmware revision, and similar relevant information about the laser. If that exact combination had not been previously tested, the speed measurement would be inadmissible.

Even in DUI cases where the stakes are much higher defendants have had limited success with the firmware version argument. Traffic court is supposed to be an assembly line. The goal is consistency: same ingredients, same process, and same result in every case. Arguing over lasers or breathalyzers does not promote that goal.

Try to get these details on the record in traffic court, but don’t be too optimistic.

How many miles per hour in a yard?

The Fourth Circuit opinion misunderstands how people think.

A police officer was using traffic stops as a pretext to search for drugs. He testified that he saw a car going 75 in a 70 zone. If his observation was accurate, he had probable cause to stop the car. If not, the evidence would be thrown out.

The defense attorney did a good job of cross examination, tripping up the officer on facts like the number of inches in a yard. The appeals court ruled that speed is the result of dividing distance by time, and misunderstanding distance was the same as misunderstanding speed.

You probably know how fast you are driving without looking at your speedometer. I doubt you count seconds between dashes on the pavement and multiply by 30 feet between dashes and divide by 5280 feet per mile and multiply by 3600 seconds per hour. Based on your experience you have a sense of how fast the scenery is moving and how loud the engine is.

If the officer had measured the number of inches or yards and used a calculator to determine speed his mistake would be material. He did not. He testified based on his experience. He did not divide distance by time any more than a baseball outfielder does calculus. The outfielder runs a feedback loop that experience says will put him under the ball.

The result is right. A visual estimate of 5 mph over the limit should not be good enough on its own. The logic is wrong.

I suspect the real motive behind the court’s decision was the officer’s obvious lack of concern for the vehicle’s speed. He was looking to make a drug bust and deliberately avoided using radar,VASCAR, or pacing. A second measurement could only hurt his case.

This decision is binding precedent in federal courts in the Fourth Circuit (South Carolina to Maryland). If you get a federal speeding ticket on one of the parkways around Washington, DC you may be able to force the officer to convert car lengths to inches to furlongs until he makes a mistake. The law says a visual estimate is only as good as the officer’s knowledge of Imperial units.

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