Can we be sure Martians are against capital punishment?

As Wikipedia notes here, the term "world" can reference just the Earth or the entire universe.  Because I suspect that the organizers of today's "World Day Against the Death Penalty" are eager to give the term its broadest meaning, I am left wondering how we would know if life on other planets might be for or against capital punishment.  (Of course, if there is the death penalty on other planets, I suppose the certain terrestrial prison officials will be eager to find out if any aliens have devised an execution technology superior to lethal injection.)

Astrophysics and metaphysics aside, I suppose it is fitting that the Supreme Court is honoring this worldly day by hearing oral argument in Medellin v. Texas (06-984), a capital case examining the President's power to direct Texas courts to comply with a judgment of the World Court concerning the Vienna Convention on Consular Relations.  SCOTUSwiki has effective coverage of the case here.