There is an evil resulting from the employment of death as a punishment which may be properly noticed here.---It destroys one source of testimonial proof. The archives of crime are in a measure lodged in the bosoms of criminals. At their death, all the recollections which they possess relative to their own crimes and those of others perish. Their death is an act of impunity for all those who might have been detected by their testimony, whilst innocence must continue oppressed, and the right can never be established, because a necessary witness is subtracted.
Whilst a criminal process is going forward, the accomplices of the accused flee and hide themselves. It is an interval of anxiety and tribulation. The sword of justice appears suspended over their heads. When his career is terminated, it is for them an act of jubilee and pardon. They have a new bond of security, and they can walk erect. The fidelity of the deceased is exalted among his companions as a virtue, and received among them for the instruction of their young disciples, with praises for his heroism.
In the confines of a prison this heroism would be submitted to a more dangerous proof than the interrogatories of the tribunals. Left to himself, separated from his companions, a criminal ceases to possess this feeling of honour which unites him to them. It needs only a moment of repentance to snatch from him those discoveries which he only can make; and without his repentance, what is more natural than a feeling of vengeance against those who caused him to lose his liberty, and who, though equally culpable with himself, yet continue in the enjoyment of liberty! He need only listen to his interest, and purchase by some useful information some relaxation of the rigour of his punishment.
RP Book 2 Chapter 12 Section 2