Q&A - Using GPS Evidence in Court

GPSQ: I was issued two tickets in June of 2018, one of them for excessive speed. I was and still am an N driver. It occurred at 142 Street and 72nd Avenue in Surrey in a speed trap. I acknowledge the fact that I was speeding but did not reach the over 40km/h threshold. I have evidence from my iPhone 8 Plus and the Life 360 app that shows the speed I reached was 3km/h fewer than 40km/h over the limit. Any advice is greatly appreciated.



This is actually a situation that I have discussed with current traffic enforcement officers in the recent past. Their response was that the court did not accept the GPS evidence in defence.

After a bit of thought, I suspect that this is because the accused did not prepare the way for the evidence. The sitting judicial justice assigns weight to evidence like this by knowing it's accuracy and reliability.

The laser speed measuring device is actually a good example of this. The officer testifies to being trained in it's use, that the device was tested and found to be operating as intended by the manufacturer and, at least when it was new, had compared speeds measured by the laser with ones taken at the same time with radar and found to be the same.

Radar had a long history of use and acceptance by the courts at that point in time.

So, if you intend to use GPS evidence to defend yourself, you would need to testify along the same lines for your GPS device.

The creators of the Life360 app did not respond to my e-mail, but their web site says that their device speed is "reasonably accurate." Further "Accuracy is determined in large part by the strength of the signal and data connection to the app. A weaker signal will produce less accurate results."

I use eDriving's Mentor app to monitor my driving. They also did not respond to my request for information.

I am aware that BelairDirect insurance requires the use of their AutoMerit app as part of their policy. I telephoned their customer service and was told that the app was "really accurate." Unfortunately the lady really had no idea what that statement actually meant. She passed me off to their technical support for the app but they chose not to respond to my query.

My dash cam also records my speed, but again, it's up to me to show it's accuracy as the manufacturer is of no help.

I wonder how often these apps sample the speed and if it is reported as measured or averaged between samples.

Now, you might think that comparing your device to the reading on your speedometer would be a good thing. Yes, that's not a bad idea, but now we're left with the question of how accurate is your speedometer? Unless you can satisfy the court that both your speedometer and the comparison is accurate, we're not much further ahead.

Using a roadside speed reader board as a comparison also has it's hazards.

Where does that leave the average driver with all this? Not too far ahead. While you may be able to raise some doubt, it would be very difficult to refute police speed measurements.

In this case, since only 3 km/h is involved, drawing attention to the accuracy of the police measuring device and explaining your GPS measurement may be enough to drop you down by those 3 km/h and into the lesser expensive speeding bracket.

Beware being a GLP driver and using GPS as well.

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