We've had this argument roughly 6-monthly on a regular basis.
My reasoning is that the likes of Roy Whiting, Ian Huntley, Mark Bridger et al most definitely ought to be executed. But modern society ought not carry out state murder etc blah, blah, blah, blah.
How can patients be denied life saving/prolonging medicines as a result of cost cutting measures and cutbacks, yet those who commit the most heinous crimes imaginable get 3 meals a day, roof and access to amenities etc? Centres of excellence that are pioneering treatment for children have to rely on charity, like G.O.S.H. and the like, whilst the vermin of society languish behind bars.
This is the modern era, where every government department suffers cuts year on year. Those cuts ought to include the execution of those who cannot and will not ever be rehabilitated.
As for the Timothy Evans case, sad and cruel though it was the advancements in forensic science and current Police legislation regarding the questioning of suspects mean that in this day and age he would never have even been a suspect.