One "solution" that strikes me is where an event requiring confirmation occurs, requesting back-up evidence from anyone who has it. More suitable for events that happen in a public space, of course, but the number of people routinely imaging their daily life is such that this could be feasible - this would not just be about visual images, sound would be necessary too. The task of stitching together disparate sources to prove chronology would be a monumental feat - which is its advantage, because those that aim to fake the evidence will need to fake the physics too: taking into account such things as the speed of sound between two device recordings sited at different points around the audible area, for instance. Wind direction and position of clouds affecting the lighting of the scene would also need to be taken into account, which is technologically out of scope at present, but if deemed important enough, will need to be considered.
I think that attempts were made to carry out such detailed analysis (within the confines of the technology of the day) were carried out subsequent to Kennedy's assassination, for example, despite it being later discredited:-
Then there is the analysis Inmarsat did for helping to determine the fate of MH370.