Gawd, Indians are naive. ISI and by proxy the Islamic establishment in Pakistan, is a state within a state. It does not hesitate to go after its own (Pakistani) leaders/citizens when it sees that they are not working for the strategic goals of the Islamic Ummah. Since their defeat at the hands of a Kafir (Hindu/Sikh) Indian army in 1971, every ISI operation has been directed towards achieving a efficient Jihad worldwide with specific focus on Kafir India.
Initially, the US, like a ignorant fool supported the ISI hoping that it will be a pawn against Communist USSR. Later the Americans and the rest of the world realized the true nature of Islam and the blunder they commited by helping ISI become a monster.
The question of trusting ISI does not arise. India trusting ISI is like Prithviraj Chauhan trusting Mohammad Ghori....AGAIN.