For a murder charge you don't require intent to kill: Intent to inflict grievous bodily harm is sufficient. My recollection is that if you're trained in combat sports (particularly boxing) your fists can be regarded legally as a weapon, making intent to inflict grievous bodily harm plausible and a murder charge possibly sustainable. Irrespective, in all murder cases a jury has the right to find not guilty for murder but guilty of manslaughter.
