They didn't have a handwriting expert to analyze it. The family (through the lawyer) complained about that.
I think this definitely should have been looked into. However, I still agree with this (I'm assuming block leters means writing in all capitals)
http://handwritinganalysis-1.blogspot.com/2009/03/when-people-write-in-all-capitals.html
The least possible is revealed from writing in all capitals. Printing shows less than script, but when all the writing is in capitals, it hides even more.
Most handwritten ransom notes, for example, are written in all capitals!
I think finding a note or using any written evidence related to a death/murder that is in all printed caps is immediately suspect since it is much more difficult to know who wrote it.