I'm glad Alexander Blackman is to be freed – and I'm glad he went to jail

Alexander Blackman – 'Marine A' – has been sentenced to seven years for diminished responsibility manslaughter. He could be free in weeks.

The back story is well known in Britain. Blackman was convicted of murder in 2013 after he was tried on the basis of helmet camera footage showing him shooting dead a wounded Taliban fighter in Helmand in 2011. He was a highly experienced soldier who had seen fierce fighting over a prolonged period. The appeal court found he had been suffering from 'abnormality of mental function', a mental illness caused by combat stress.

British troops fought fierce battles in Helmand province, Afghanistan.Reuters

It would be nice to say the case had divided opinion, but that's hardly true. Most commentators, and the vast weight of public opinion, was on his side. Most people seemed to think his original conviction for murder was just outrageous: the enemy's the enemy, the Taliban are truly bad people and one fewer of them makes the world a slightly better place. Manslaughter on the grounds of diminished responsibility is a bit better, but he should still never have been sent to prison.

Well: I want to argue, in the fullest and most sympathetic awareness of his plight, that the law of the United Kingdom – belatedly – got it right, and that this reflects its Christian foundations.

Terrible things happen in war. It's only in recent years that there has been a thoroughgoing attempt to lay down rules about what soldiers can and can't do to their opponents. It's frustrating for them, but there it is. In the First or Second World Wars, what Blackman did would have been routine. Wounded enemies were treated where practicable, despatched where not. It's war, not a BBC Question Time discussion. And – obviously – the experience of being under fire, for weeks or months, facing a deadly enemy fighting without any of the moral or legal scruples of the soft and civilised West, is going to challenge those scruples. But that's what the law is for: to say, 'No'. 

In a Panorama documentary about the case directed by Chris Terrill, who went through Royal Marines training himself in order to understand, as far as possible, their mindset, his colleagues supported him. One said: 'Everyone wanted that guy to be dead. I'm glad Al did what he did, because all my guys went home.

'And maybe just maybe if he hadn't of done that I'd have been going to a few more funerals or laying some more flowers on people's graves, for someone I have absolutely zilch respect for because he was trying to kill my friends and me.'

He also said: 'After that repetitive exposure to violence and different cultures, I'd changed.'

With testimonies like this – and the loyalty and commitment shown by Blackman's wife, the admiration for the courage shown by British soldiers and the widespread public perception that they shouldn't have been in Afghanistan in the first place – it's easy to slip into thinking Blackman was just, well, right. But he wasn't.

What's missing from this account is the voice of the victim – and someone has to speak for him. Christians resist the idea that there is only one side to a conflict, that the world is divided neatly into 'us' and 'them', with all goodness and righteousness on our side. We do this even in the context of warfare. Blackman – and his colleagues – were under huge strain, of a kind that can't be imagined by people who haven't experienced it. No one should quarrel with the appeal court's judgment or doubt the evidence of psychiatrists who have said Blackman was ill.

But what has decades of war done to the Afghan 'enemy'? There are no psychiatrists to diagnose battle fatigue or PTSD among the Taliban. They are simply assumed to be evil. The experiences that formed them are deemed irrelevant. But Christians want to say that they, too, are made in the image of God. They are not just targets, they are people – and if they do terrible things, we need to be willing to ask questions about why that might be, just as we do in the case of our own.

The law is a blunt instrument at best. Alexander Blackman's sentence will seem too harsh for some, too lenient for others. But the court sent a signal that it's wrong to kill – to kill anyone – when you don't have to, and in doing that it underlined a fundamental Christian truth. As the prophet Malachi says: 'Have we not all one Father? Did not one God create us?' (2:10).

Follow Mark Woods on Twitter: @RevMarkWoods