A lorry driver claimed a stranger walked up to his truck at a service station in Greece and threw him two holdalls full of heroin.
The High Court in Glasgow heard Peter Cameron, 37, was then told: "Drive carefully."
He was giving evidence at the trial of Russell Stirton, 57, of Milngavie, East Dunbartonshire.
Mr Stirton denies being concerned in the supply of heroin in the UK, Italy, Belgium and Greece.
The allegations date from 23 September to 26 November, 2012.
Consignment of breadsticks
Former soldier Cameron was jailed for six years in Bari, Italy for trafficking the "substantial quantity" of heroin.
He told prosecutor Alex Prentice QC that he was asked at the last minute to go on a work trip to Europe with trucker Samuel Wilson.
He said they dropped off a load in Rome, Italy and then drove to Greece to pick up a consignment of breadsticks.
Cameron told a jury that on 22 November, 2012 they parked at a service station somewhere in Greece.
Asked what happened, Mr Cameron told him: "A Mini drove in.
"Mr Wilson got out the cab and someone got out the Mini.
"The passenger door of the truck was opened by a man who threw two green holdalls up to me.
"I was told to drive carefully twice, then the door was closed and interior light went out."
Blocks of heroin
Cameron said that when he looked in the holdalls later he found blocks of heroin.
He claimed that he had nothing to do with the heroin and tried to tell the authorities in Bari what had happened, but alleged they would not listen.
In his evidence, which was given via a video link, he said that Mr Wilson hid the heroin among the load of breadsticks and then they drove to Italy.
They were both arrested in Bari when they docked from the ferry from Greece.
Both were sentenced to six years imprisonment.
The court heard that in August 2015 Mr Cameron was asked by Police Scotland to have a look at a sheet of paper with a number of images on it and see if he could identify the man who threw the heroin to him.
Mr Prentice asked Mr Cameron: "Did you think about the matter carefully?"
He replied: "I did.
"To be honest I didn't want to pick out the person and thought about picking out someone at random.
"I did the right thing and chose carefully."
The jury has heard that Mr Cameron picked out image number five, but has not been told who that person is.
When questioned by the authorities in Italy, Cameron told them: "I don't know when the drugs were loaded on to the lorry."
He was also asked if he knew there were Class A drugs on the lorry and replied: "Yes, I did indeed."
Defence QC Brian McConnachie put it to Cameron: "Either you were lying when you were in Italy being examined by magistrates or you are lying now."
Cameron replied: "I said that in Italy because I was told by my lawyer if I didn't do what he said I was looking at a 20-year sentence, not a six-year sentence."
The jury has been read a joint minute of agreement that states that Mr Stirton flew into Athens, Greece from Brussels on 20 November 2012 and flew back out from Athens to Brussels on 26 November.
The trial before Lady Rae continues.