Having read the article Guy Paul Morin, this happened back in 1984 & it was developments especially in DNA that secured his release & acquittal in 1995. So from that viewpoint we are now in 2011 DNA matching along with other bettered forensic techniques & video evidence are pretty effective in ascertaining guilt/non guilt that we can agree on.
So with this in mind a fairly strong case can be presented allowing for a cast iron decision for or against. Should the crime involve a pre meditated murder or someone armed having every intention of using a weapon in their illegal activities these are the kind of people the "Hanging verdict" should be applied to.
"The Death sentence is not a deterrent" I beg to differ, Singapore as an example, the Death sentence is on the statutes & is used effectively within a short period of time so reinforcing the, severity of punishment in relation to the crime so people think twice. The States on the other hand drag the whole legal process out over years & years so reducing the "Shock & awe" swift retribution effect so isn't readily seen as a deterrent.
Had A hanging verdict been available in UK & the will to use it perhaps some of the following incidents wouldn't have happened :-
Police killer caught on London jaunts - Telegraph
Police hunt missing killer as woman's body is discovered | UK news | The Guardian
BBC News | UK | Freed killer murders again