If you can hear the co-pilot clicking the door lock button, that is direct evidence.
If you could hear him in an anxious state breathing heavily as I imagine someone in the process of murder would be ... that would also be direct evidence.
Otherwise it is all imagination.
Perhaps people like to imagine that life is a big disaster movie.
Rather the mundane truth that accidents happen.
A number of planes have gone down recently with no-one found responsible ... it is starting to look like no-one is really in control and life is precarious.
And maybe that is simply the truth.