The sentencing remarks state that the court felt it important to send out a strong deterrent message. Service personnel who commit crimes of murder, or other war crimes or crimes against humanity while on operations will be dealt with severely. The deterrent message was also intended to reassure the international community that allegations of serious crime will be dealt with transparently and appropriately.
This message was, in the court's view, delivered by the sentence of life imprisonment (mandatory for murder). Setting the minimum term reflects the seriousness of the offence while taking account of the unique and special circumstances of the case and personal mitigation.
Interestingly, Judge Blackett also commented that the defendant had been judged by a 'Board made up of Service personnel who understand operational service because they too have experienced it. That is one of the strengths of the Court Martial system.'
An order of the Court Martial permitting the marine to be anonymous was lifted - Judiciary UK - Orders of 5th December 2013