Difficult to prove in my opinion. Most of the evidence would be confessions from low-level operatives of the TTP, that would be looked at with doubts.
The reason India was successful was because of the open admission of Hafiz Saeed and his ilk and the public attempts to recruit people.
In cases where India has attempted to provide evidence, much of it has been questionable as well. If you recall, often the modus operandi of such evidence was always an "ID card" of a terrorist organization and a "diary" that contained juicy details that required the imagination of a fiction writer.
That depends on whether it is a trial by media or a trial by court. In court you need real evidence.
You can check the judgement at https://nia.gov.in/writereaddata/Portal/CasesPdfDoc/2016-12-19---_judgement_of_court-2.pdf for the dilsukhnagar twin blast case. https://nia.gov.in/case-detail.htm?93