What sort of thing would you expect?
I'm really not getting this.
location and travel data is on all phones... GPS could be overlaid on a gps 3d history , per day, location and time along with data transfer items, meta data to determine who he actually had been talking to... for example
if I were investigating I would be using those kind of “tools” in order to identify and expose who this killer was and whose company he kept or perhaps determine those who inspired him.