The Joseph Packer (convict) would appear to be the Ticket of Leave man Joseph Parker mentioned in the file newspaper clipping attached.
He shot himself by accident in Guildford 13.4.1852 and reported in 'The Inquirer' 21.4.1852.

Note the incorrect name in the newspaper..
As far as I can see there was no convict Joseph Parker sent to W.A.

Therefore it would appear that the convict is not the man you are following.