A lorry driver opened a text message seconds before he veered into oncoming traffic and caused a crash which killed a police officer, a court heard.
Danny Warby, 28, was driving the 13.6-tonne light goods vehicle along the A141 in Cambridgeshire when he opened a text message on his phone, said Helen Guest, prosecuting.
His vehicle crossed the white line in the centre of the road and clipped an oncoming lorry, showering two cars in debris, before crashing into a Renault Clio which was also in the oncoming line of traffic, Peterborough Crown Court heard.
The Clio was driven by Cambridgeshire police officer Sharon Garrett, a married mother-of-two who was on her way home from work. She was pronounced dead at the scene on June 6 2014.
Warby denies a single count of causing death by dangerous driving.
Ms Guest said: "Mrs Garrett, in the short time available to her, had started to take evasive action towards the grass verge as the lorry headed towards her, but she was unable to prevent a collision.
"Both vehicles landed on their sides in a ditch at the side of the road."
Ms Guest said Warby, of School Road, Runcton Holme, King's Lynn, had opened a text message on his phone one minute and six seconds before the time of the crash, with the precise time of the crash established by tracking data from the lorry.
She said he had no hands-free kit or cradle for the phone in the lorry.
"It's possible he didn't read the text immediately, just opened it," she said.
"After all, after (he drove past) the safety camera there was a bend and you have to steer round bends and in the meantime after opening the text, where was the phone?
"What was he doing with his hands, what was he thinking?
"The collision took place on a fairly straight stretch of the road, that's the irony.
"After all the bends and junctions and the more dangerous manoeuvres, this accident happened on a relatively straight stretch of road, when, if a person might be that way inclined, it might present an opportunity to read a text."
She added: "If you're interacting with a mobile phone, your eyes aren't on the road and your two hands aren't on the steering wheel."
The fatal crash happened close to RAF Wyton, near Huntingdon, a 12-strong jury heard.
Warby had completed several short journeys that day in the lorry which was carrying a crane and construction materials.
The final journey, which ended in the crash, totalled less than one-and-a-half miles from the Warboys layby where Warby had parked for more than an hour, the court heard.
"That journey is going to be under the microscope during the course of this trial," said Ms Guest.
She said conditions were good, vehicle defects were not a factor and Warby's lorry was travelling at 53mph on a stretch of single carriageway restricted to 40mph for lorries at the time of the collision with the lorry.
He performed an emergency brake after the collision with the offside of the oncoming lorry, causing his vehicle to arc into the path of the blue Renault Clio.
Ms Guest said Warby had been diagnosed with obstructive sleep apnoea in late 2015 and his defence lawyers would argue that Warby experienced a micro-sleep just before the crash.
The prosecution case is that Warby's reaction to apply the brakes after the first collision was "rapid", and not consistent with a person who had been asleep, said Ms Guest.
The trial continues.