An 83-year-old man was killed and his wife seriously injured when a lorry crushed their car after changing lanes on a motorway, a court heard.
HGV driver Pavel Slabej, from Slovakia, was travelling north on the M1 by junction 13 for Bedford when the crash happened on 11 March at 11:10 GMT.
The prosecution claims he failed to look properly as he moved lanes.
The 37-year-old denies causing death by dangerous driving but admitted causing death by careless driving.
He also denied causing serious injury by dangerous driving.
Mr Slabej's lorry hit the grey Toyota Avensis driven by John Bennett.
The car was spun around in front of the lorry and crashed into a barrier before it was crushed by the lorry's trailer.
The couple, from Appleton in Warrington, Cheshire, were both seriously injured.
Mr Bennett was taken to hospital by air ambulance and later died. Elizabeth Bennett, 78, was taken to hospital with serious injuries.
Mr Slabej told Luton Crown Court he moved across the carriageway as he thought he was in a lane that would take him off the motorway. He said he checked all four mirrors in his cab before changing lanes.
His barrister Adam King asked: "Did you see any vehicle?"
Mr Slabej said: "At the time no. I put on my indicator, checked my mirrors and started to go to the next lane."
The lorry driver told the court he felt "terrible" about the fatal crash.
"What happened is not supposed to be happening. It is terrible. I don't know how to say how sorry I am for what happened," he said.
The trial continues.