I do not really know, but ...
Ghost Ryder: While more evidence is required to take action, it seems to me to be clear that Islamics are behind this atrocity.
In the last 100 years, two cultures have endorsed Kamikaze methods. I do not think the Japanese are behind the attacks, so where else would you look for suicidal killers of innocent people?
The race is not always won by the fastest runner, and the battle is not always won by the fiercest warrior, but that is the way the smart money always bets.
If you had to bet on who planned these attacks, who you put your money on? Hindus from India? Russians? The US White supremacist nuts? Perhaps we should investigate the Chinese.
I think the odds are damn good that it was a group of Muslims based in an Islamic country. If I were running the investigation, I would put the best and the brightest to work on checking the Islamic countries, and assign a few journeymen to investigating other possibilities.
BTW: When there is war, due process is no longer applicable. That is for peace time application when dealing with ordinary citizens. I would not require proof beyond a reasonable doubt before going after terrorists. I would go after anybody who voiced approval of the attacks.