2011 Helmand Province killing

The 2011 Helmand Province killing was the manslaughter of a wounded Taliban insurgent by British Royal Marine Sergeant Alexander Wayne Blackman on 15 September 2011. Blackman and two other Royal Marines, Corporal Christopher Glyn Watson and Marine Jack Alexander Hammond, known during their trial as Marines A, B, and C, were anonymously tried by court martial for the killing. On 8 November 2013, Watson and Hammond were acquitted, while Blackman was found guilty of murder of the Afghan insurgent in contravention of section 42 of the Armed Forces Act 2006. This made him the first British soldier to be convicted of a battlefield murder whilst serving abroad since World War II.

On 6 December 2013, Blackman was sentenced to life imprisonment with a minimum term of ten years before being eligible of parole, and dismissed with disgrace from the Royal Marines. On 22 May 2014, the Courts Martial Appeal Court reduced his minimum term to eight years.

A campaign in the Armed Forces community tried to have his conviction overturned, led by Claire Blackman and the MP for South Dorset, Richard Drax. During the campaign to free him, the Criminal Cases Review Commission concluded that Blackman's defence team fell "way below the standard expected". At the subsequent appeal hearing in 2017, the conviction was overturned and the hearing stated that "At the time of the killing the patrol remained under threat from other insurgents... Given his prior exemplary conduct, we have concluded that it was the combination of the stressors, the other matters to which we have referred and his adjustment disorder that substantially impaired his ability to form a rational judgment."

In March 2017, the conviction for murder was overturned and reduced to manslaughter on the grounds of diminished responsibility. Blackman was released from prison on 28 April 2017 but his dismissal from the Marines remains in place.