Petition Referendum on Return of Capital Punishment

First of all, a referendum on whether to re-introduce Capital Punishment, but only for a system of two-degree murder, where a conviction for first-degree murder would carry a mandatory death penalty. A conviction for second-degree murder would not carry a death penalty.
Two examples: the pre-meditated killing of a partner's's lover would, in my view, be classed as second-degree, whereas the non-premeditated killing of an innocent passer-by during a shop burglary, would, in my view, be first degree. This is quite contrary to the old system, which I would not want to see brought-back, and in a referendum, this is the only sort of question I would vote in favour of..