Pc John Dougal denies causing death by dangerous driving
A policeman's decision to accelerate to 90mph shortly before he hit and killed a schoolgirl was "disproportionate", Newcastle Crown Court has heard.
Pc John Dougal denies causing death by dangerous driving over the crash which fatally injured Hayley Adamson, 16.
Police driving expert Gordon Robertson told the court he could not imagine a situation where Pc Dougal should have driven at the speed in the 30mph zone.
The patrol car's siren and lights had not been activated, the court heard.
The crash happened on Denton Road in the city's west end on 19 May last year.
The jury has been told that Pc Dougal was reacting to the Volvo's automatic number plate recognition system, which alerted him to a passing car - indicating it could potentially be linked to a crime.
Pc Dougal accelerated to catch up with the Renault Megane, and struck Hayley when she stepped into the road.
The number plate data was later found to be out of date, the court heard.
Schoolgirl Hayley Adamson was killed instantly
Retired police inspector Mr Robertson told prosecutor Andrew Dallas that driving the marked Northumbria Police car at 90mph posed a significant danger.
He said: "As far as driver skills go, if you propel a vehicle at a speed of that magnitude you reach a point where physics decides if you can stop it and not you.
"Sadly, on this occasion it appears that was so. There are dangers to driving fast and sometimes there can be justification for a good degree of risk.
"There can never be a justification for the ultimate risk - to drive to the point where you effectively become a passenger in a car you are supposed to be driving."
He said that for the Northumbria Police traffic officer to have done so meant his training had failed.
Mr Robertson added: "When an officer decides that they are going to use their lawful legal exemption from the speed limit it must be forefront in their minds what type of road they are on.
"You do not just automatically view every road as if it was a national speed limit road over the fells in the middle of nowhere. It never becomes irrelevant."
The trial continues.