Thompson Jnr was shot dead outside the family’s Blackhill home in August 1991.
Ferris’ trial, which began the following year, was described at the time as the longest and most expensive criminal case in Scottish legal history.
More than 300 witnesses gave evidence during the 54-day proceedings, which were estimated to have cost £4m.
The prosecution case relied heavily on the evidence of Dennis Woodman, who claimed Ferris had confessed to the killing while both men were being held in Barlinnie Prison.
Defence lawyers challenged the credibility of the evidence and argued the case against Ferris was deeply flawed.
After more than 24 hours of deliberations, the jury acquitted him of murder and all other charges in 1992.