It is a sign of the gulf between the military and civilian arms of our society that five appeal judges can sign off a judgment which refers to a helicopter firing 139 rounds of '130mm ammunition’ at insurgents. Nato does not use 130mm ammunition, least of all in choppers. The formidably lethal Apache helicopter carries one 30-mm gun.   

Luckily the trivial transcribing error in the Courts Martial Appeal Court's judgment in R v Alexander Wayne Blackman had no bearing the process of correcting the injustice done to former sergeant Alexander Blackman. By overturning the original court martial's verdict of murder with one of manslaughter by reason of diminished responsibility, the appeal enabled the passing of a prison sentence which should lead to the former Royal Marine being freed in a couple of weeks. 

Other symptoms of the military-civilian gulf may be more relevant, and not just to the Blackman case. Over the past three years, legal London has become used to demonstrations by Blackman's supporters - taciturn elderly men with racks of medals pinned to their overcoats and hard-faced younger types sporting green or maroon berets along with jeans and leather jackets - outside the Royal Courts of Justice. Black cab drivers tooted their support, but legal and academic London, the epitome of the liberal metropolitan elite, in the main passed warily by. Blackman wasn't our cause. 

He should have been. The 37-year-old sergeant was on our payroll when he was put in command of Command Post Omar, deep in hostile territory, with no commissioned officer on hand - or even visits from the padre, as the position was deemed too dangerous. The narrative of the appeal judgment reads like a treatment for a classic war film, in fact the tale of an exemplary veteran being pushed over the edge by combat and then apparently being hung out to dry by the establishment would be dismissed as too much of a cliche if it were not for real. 

In this story, observers from both sides of the gulf can share feelings of both shame and pride. 

The shame has to start with the hard fact that the 'killing by shooting of an injured insurgent... in contravention of the Geneva Conventions', as the judgment puts it, let down the values for which the International Security Force and HM Armed Forces were sent to Afghanistan. The subsequent inadequacies of the court martial process, in particular over the calling of psychiatric evidence, should also be common ground for shame.

What pride can be salvaged from this sorry incident? Simply that there are two sorts of jurisdictions in the world, those that prosecute their own soldiers for frontline crimes against the enemy and those that do not. Friends of justice can be proud that the UK has shown itself to be in the first group. It's a select club; the only other country to have demonstrated its membership lately seems to be Israel, which last month jailed a 20-year-old sergeant for the manslaughter of a Palestinian lying wounded after attacking an Israeli soldier. And Elor Azaria's 18-month sentence for what many will regard as a more culpable offence was considerably lighter than Blackman's seven years.  

The UK should of course remain a member of this club. But the terms of membership will have to be understood across the military-civilian gulf better than they are at the moment. Especially as the technology of the helmet-cam has eroded the old code of omerta about what really happens on battlefields.