Complex sentence: The group is put on trial and their history is reviewed, which eventually reveals that the diary is a hoax created by Batman in an effort to have the JSA apprehend Per Degaton at a future time that Batman believed he would not be alive for.
Split into simpler sentences: The group is put on trial and their history is reviewed. It eventually reveals that the diary is a hoax created by Batman in an effort to have the JSA apprehend Per Degaton at a future time that Batman believed he would not be alive for.