With his fear of the police & obsession with being hanged, I'd say it was unlikely.
But he'd probably say 'it's a shame Myra Hindley & Ian Brady missed the death penalty by a year' - because everyone's older relatives say that. Just like they complain that decimalisation put the prices up & Christmas starts earlier every year.
This is a really interesting question.
I think that only means that he believes that there are people in this world who deserve to die. He's so mistrustful of the government and authority that I cant imagine him supporting the idea of the law deciding who deserves to die, especially seeing as many of the people he's wished death upon in the past have been agents of the law/ government.
I think it's a bit like the free speech question. He's quite ardently pro free speech. The fact that he's personally wanted to silence people in the past doesn't change that fact. He won't tolerate hecklers at his shows and wanted to close down this site because he doesn't like taking abuse from people, but ultimately he doesn't trust the government to regulate what we can and can't say.
Except insofar as he likes, in the style of an adolescent, still to be contrary and irritating to grown-ups, Morrissey's not exactly noted for his hallmark consistency. For that reason - and supposedly liberal predisposition aside - capital punishment is precisely the kind of f_ckwitted thing he would advocate.