It is much easier to project such a message upon the dead...
I seem to recall certain phone calls being received by relatives of the passengers who who died on 9/11 - not 'entirely' sounding like themselves (sufficiently so for certain relatives not to believe that such calls were genuine).
Perhaps this technology has been around longer than one might think?
The only defense that a person has in this World of sordid interests - is a proven track-record that flies in the face of irreconcilable new information.