A group of men found guilty of shooting dead an Adelaide man at his workplace have had their convictions overturned and will face a retrial.

Jason De Ieso was gunned down at his Pooraka workshop, Unique Custom Paint and Panel, on November 21, 2012.

WATCH ABOVE: Men found guilty over shooting of Adelaide man have their convictions overturned.

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It is alleged that he was an innocent bystander who was shot during escalating violence between the Finks and Hells Angels outlaw motorcycle gangs.

Police believe the intended target was a senior member of the Finks, who was a frequent visitor to De leso’s workshop.

It took five months and six days to convict the seven men of murder, making it one of SA’s most expensive murder trials.

All men were served with life sentences.

Brothers Husain Alzuain, 37, of Goodwood, Mohamed Alzuain, 33, of Mile End were given 35 years of non-parole.

Musa Ali Alzuain, 32, of St Morris, Daniel Mark Jalleh, 36, of Clovelly Park, Ross William Montgomery, 40, of Andrews Farm, Kyle Lloyd Pryde, 36, of Adelaide and Nicholas Sianis, 38, of Beverley were all served with a non-parole period of 30 years.

A verdict was unable to be reached for one accused man while a ninth died before the trial was brought to court.

President of the Court of Appeal, Justice Mark Livesey, only gave the appeal the green light on “directions on joint enterprise”.

Joint enterprise legally refers to a situation where two or more people agree to commit a crime, and each is held responsible for the actions of the others in carrying out that crime.

It means that if a group plans or participates in illegal activity, everyone involved can be held accountable for the actions of the others, even if they didn’t directly participate in every aspect of the crime.

All seven men argued in their appeal they were unfairly treated as a collective.

A retrial date has yet to be confirmed.