For what it's worth, if anybody commits a crime in a country that they're "not from" then they should, once they've served their time for the crime, be deported back from whence they came. The punishment for the crime, should be served in the country the crime was committed, to ensure that justice is actually served properly. Once you go back to your country of origin, if they decide they want to kill you and you family, well that's just tough shit.
For me, the big issue is what to do when the country the criminal originally comes from decides they don't want them back, as can happen (Shamima Begum for instance...)