John Locke, Immanuel Kant, and George Wilhelm Friedrich Hegel all championed the death penalty.
Intellectuals of the modern era have spoken out against the death penalty.
Why the sudden shift in academic circles?
The philosophers of the Enlightenment of the Romantic Movement still championed hierarchy, unassailable. Law as organic example must hold full sway over a community. Outside of tradition and history, and respecting contract as precursor to community, political philosophers regarded human beings as mere agents of a rational, perfectible order.
Fast-forward to today, there is little reference to the perfectibility of man or his role in the state. The recognition of the state's fallibility as an engine of justice has caused many thinkers to pause over the finality of capital punishment, This leniency springs from the growing disdain of the dichotomy between acceptable and unacceptable, right and wrong. In an arena where equality has become the sine qua non of a just society, intellectuals will not tolerate the ultimate hierarchy of one man, or the state, taking the life of another.
The dialectic of state power has given way the fundamental challenge to a unitary order — this explains the shift in regards to the continuance of the death penalty.