Since his teenage years, Koji Hayashi has dreaded one thing: his stubborn, once-vivacious mother Masumi being hanged for murder after failing to win her long campaign for a retrial. Masumi Hayashi, 63, is notorious in Japan for a crime she swears she didn't commit -- killing four people by putting arsenic into a pot of curry at a summer festival in 1998. Left almost unchanged for a century, Japan's current retrial system is often labelled the "Unopenable Door" because the chances of being granted a legal do-over are so slim. But hopes have grown of a change since a court last year overturned the wrongful conviction of the world's longest-serving death row prisoner Iwao Hakamada, whose case took 42 years to be reopened. IMAGES AND SOUNDBITES ARRANGED IN SEQUENCES