In cases of murder,rape and pedophilia, when the criminal has been proven guilty beyond doubt, I don't see the reason in humiliating and displaying corpses. In fact this was a vile practice of those who opposed the Prophet(Peace be upon him) That they would leave bodies hanging and/or mutilate them as a means of intimidation.
As for deterrent etc,then the fact that the death penalty exists should suffice, no need to do anything opposing to the Shari'ah assuming it to bring better results!
And finally yes, the murdering prince should have long ago met his Waterloo, and it's saddening to see the level of injustice for which reason he still is alive and kicking unlike his unfortunate victim!