On 14 May 1752, Colin Roy Campbell of Glenure — a Clan Campbell tacksman acting as government factor for the Forfeited Estates Commission — was shot in the back and killed while riding through the wood of Lettermore near Duror, in the Appin district of Lochaber, Scotland. Campbell had been overseeing mass evictions of Clan Stewart of Appin tenants from confiscated Jacobite estates, replacing them with Clan Campbell tenants, and was travelling to enforce another eviction when he was killed. He was accompanied by three mounted companions, including his nephew Mungo Campbell, who reported sighting an armed figure on a hillside after a single shot was fired. Campbell reportedly cried out "Oh, I am dead! Take care of yourselves!" before dying.
The investigation focused on Clan Stewart. The initial chief suspect, Alan Breck Stewart, fled and was never tried. James Stewart of the Glens, the de facto chief of Clan Stewart, was arrested two days after the killing and prosecuted for murder "in airts and pairts" (as an accessory before the fact) despite trial testimony indicating he had an alibi placing him miles from the scene at the time of the shooting. The trial was presided over by Archibald Campbell, 3rd Duke of Argyll, chief of Clan Campbell, and the jury contained a majority of Campbell clansmen. James Stewart was convicted and hanged on 8 November 1752 at Ballachulish, protesting his innocence to the end. His remains were left displayed at the site for eighteen months as a warning to other clans.
The case has long been regarded by historians and legal commentators as a significant miscarriage of justice, and it inspired elements of Robert Louis Stevenson's novels Kidnapped and Catriona. Subsequent research has produced competing theories about the true identity of the shooter. Ian Nimmo's 2005 investigation, using forensic analysis of contemporary post-mortem reports, concluded the fatal shots were fired from close range at a low position on the hillside rather than from the distant figure Mungo Campbell reported seeing. In 2001, Amanda Penman, a descendant of the Stewart clan chiefs, alleged the killing was carried out by Donald Stewart of Ballachulish following an informal shooting contest among four Stewart tacksmen, a claim she said was supported by local oral tradition. Historian James Hunter's 2001 book concluded that James Stewart had in fact ordered the assassination to protect his clan's interests. In 2016, academics Allan MacInnes and Mhàiri Livingstone proposed an alternative theory implicating Mungo Campbell himself, citing his motive to inherit the factor position and his control over the subsequent investigation, though they acknowledged no direct proof.
Efforts to secure a posthumous pardon for James Stewart have been unsuccessful. In 2008, lawyer John Macaulay petitioned the Scottish Criminal Cases Review Commission, arguing trial transcripts showed no evidence against Stewart, but the request was denied on the grounds that the case's age made reconsideration not in the interest of justice. In 2015, the Scottish government confirmed it would not proceed with a pardon.