Last year's shooting of 15-year-old Billy Cox on Valentine's Day was particularly gruesome. Although Billy was still only a teenager, the killer cold-bloodedly aimed the gun at his chest as he stood on his doorstep on Fenwick Estate in London's Clapham North. Billy's younger sister, Elizabeth, heard the gunshot as she was arriving home. She tried in vain to save her brother's life. Worse still, the event was not...