If a state attacks, just for example, civilian hospitals (which typically do not contain valid military targets) then, in my view, the burden of proof lies on the attacking state.

Leaving aside, of course, the fact that attacking a civilian hospital, even one that has some military targets in it (say wounded combatants), would also certainly mean killing or injuring many invalid targets, and at that point you should really provide not just evidence of a military target but also evidence that you couldn't attack the target in any other way and that the target is valuable enough to justify the deaths of innocent people.

Which Israel has not done, and really, can't do. Because there really aren't many targets worth bombing a hospital for.