Adam Morrison walked free from the Court of Criminal Appeal in Edinburgh after judges ruled his conviction for causing the death of Bettina Adams by driving without due care and attention or without reasonable consideration for others must be quashed.
Lord Brodie, who heard the appeal with Lord Eassie and Lord Drummond Young, criticised remarks made by procurator-fiscal depute Alasdair Fay about the sentiments of the dead woman's husband and a comment that the not-proven verdict was a "historical hangover".
He said: "We have come to the view that there is substance in these grounds of appeal and that, as a result of the conduct of the procurator-fiscal depute and what we see as being deficiencies in the sheriff's jury directions, the appellant's conviction must be regarded as a miscarriage of justice."
Lawyers acting for Mr Morrison maintained the prosecutor made a number of improper remarks in his jury speech that were "highly prejudicial" to the lorry driver and went uncorrected by the sheriff when he came to address jurors.
Mr Morrison, 32, formerly of Cove Bay, Aberdeen, was last year jailed for 18 months and banned from driving for five years by Sheriff Gregor Murray after he was earlier found guilty of the offence, which he had denied, by a majority verdict following a trial at Peterhead Sheriff Court.
He was later freed on interim liberation pending the hearing of his appeal.
Management accountant Mrs Adams, 44, died from head injuries on January 21, 2011 after her Vauxhall Astra collided with the articulated lorry being driven by Mr Morrison at the A90 Aberdeen-to-Peterhead road.
His counsel David Moggach told appeal judges that the prosecutor at the trial had made highly prejudicial remarks that had gone unchecked by the sheriff.
Advocate depute Alex Prentice, QC, accepted that a reference by the fiscal in his speech to the jury to the feelings and sentiments of the dead woman's husband had been improper.
The fiscal Alasdair Fay said: "How would you feel, ladies and gentlemen, if you were [the deceased's husband]? He's been sat quietly through much of this trial. He should be looking ahead to Christmas with his wife."
Lord Brodie said: "These remarks were plainly irrelevant to a consideration of whether the appellant had been at fault," adding that "emphatic action by the sheriff" had been required.
Sheriff Murray had told jurors they could not be swayed by emotions or prejudices and if they felt sorry for anyone in the case they had to put that to one side.
But Lord Brodie said: "In our view, that fails to address the fact that in his address to the jury the procurator-fiscal depute had expressly and culpably invited the jury to do the contrary."
Mr Morrison's lawyers were also critical of the approach that the fiscal took to the not-proven verdict. The prosecutor told the jury it was "nobody's friend" and if they had a reasonable doubt they should find him not guilty.
He said: "It's a historical hangover which, as you may be aware, the Scottish Parliament is currently debating actually abolishing." Lord Brodie said the remarks were improper and added that three verdicts were open to a jury in Scotland, guilty, not guilty and not proven.
The appeal judges also said the prosecutor had denigrated the defence position in the trial in a way that was improper and was prejudicial to the lorry driver.