That is pretty much the level of certainty required for prosecuting crimes domestically, yes, or very close to it. Time-frame, proof of intent, and motive.
There is of course a way of doing so, as long as the attacker made a mistake. If they didn't, then it very well might be completely impossible to know who did it, and that's just how it is.
Timeframe, proof of intent, and motive are not what the commenter I replied to said, and they most certainly have those three pieces of information when attribution takes place generally speaking.
That's how I understood their comment, and in general, no, concordance of time frame and proof of intent are not proven. I think you underestimate the "proof" part of proof of intent. You not only have to prove conclusively that they did it, but back it up by proving that they intended to do so.
That's not a bar that's reached in the vast majority of criminal cases tried in the United States, or anywhere else for that matter, so it seems odd (approaching disingenuous) to try and establish that level of certainty here.
If the American justice system doesn't attempt to prove that the person actually conclusively commited the crime and has mens rea as well as a motive and a congruent time-frame to commit it, then something is terribly wrong.
There is of course a way of doing so, as long as the attacker made a mistake. If they didn't, then it very well might be completely impossible to know who did it, and that's just how it is.