20 years after subway attacks, Japan still baffled

As Japan prepared to mark the 20th anniversary of a fatal nerve gas attack on Tokyo's subway, experts say the case still leaves more questions than answers about what motivated the killings.

Thirteen people died and 6,000 became ill after the apocalyptic Aum Supreme Truth cult released Nazi-developed sarin in five subway trains during coordinated rush-hour attacks on March 20, 1995.

Despite many trials over the last two decades that have put 13 people, including cult leader Shoko Asahara, on death row, the reasons behind the shocking episode remain unclear.