I'm not sure that anyone really knows who first came up with the thought that making a casting of an executed prisoner's head was a good idea, or indeed why they thought that. Nonetheless the practice was quite common in the 1800's / early 1900's, and quite a number of them are displayed in the cells on the ground floor of the jail.

One school of thought is that it was done as an aid to the "science" of phrenology; the idea that the shape of the skull determined the behaviour of the person. Or, perhaps, vice versa.

In this case we see the death mask of George Melville, a bushranger (highwayman) who was convicted of robbery with intent to murder and hanged in 1853.His body was released to his widow who draped it in flowers, put it on public display in her oyster shop and used it as a centrepiece in her rants against the police. This resulted in a change of policy with all executed prisoners subsequently being buried in the prison itself.