First, they probably have only 50-60 Russians in custody and they are unlikely of mercenary group. Chechens are regulars belonging to the Russian national guards. Second, Ukraine is an aspiring Europeans nation and doesn’t have death penalty.
Even a pro-Russian news agency calls the Chechen scum mercenaries.
“The fighters led by the Chechen leader Ramzan Kadyrov are fighting hand-to-hand with members of the Azov Battalion resistance in the city of Mariupol. This video shows how mercenaries fighting alongside Russian troops in eastern Ukraine enter a factory in the industrial zone of Aosvstal and shoot at Ukrainian troops.”
If Russia calls these mutts mercenaries then so can a Ukrainian court and a Ukrainian firing squad.
You’re quoting the last words of a number of Russian war criminals.