If they spy swap then poison him, next time they won't get a spy swap - nobody is going to spy swap with a country that then assassinates the swapped spy. They will have gained nothing and lost an option. They will be worse off.
It is possible that the Russians are stupid, and are happy to be worse off having made a point. Stranger things have happened. But it is also possible, and indeed quite likely, they are not stupid and there is something else going on.
This is another atrocity being committed on the general public by the military industrial criminal state. Doublethink and newspeak have been very skillfully applied to ensure a lack of culpability - however, to those of us who have had to dig innocent loved ones out from under America's piles of burning rubble, it is very, very clear that the American people are responsible for this mess, whether they understand their own laws or not.
The correct answer to my question is (if you go 40 rather than 20 years) that the bodies are very much buried in Northern Ireland (although the FRU was part of the British Army)
https://truepublica.org.uk/united-kingdom/britains-secret-as...
The Russians have always been much better at espionage than the west, that's why they're bolder with these public hits.
It is indeed fuzzy
There is NO logic to violating the Universal Declaration of Human Rights, nor any of the myriad laws against extrajudicial killing, rendition and torture. It defies logic, unless the real intent is to foment the conditions ripe for yet more, endless war.
Also I think espionage is (and I think I agree, the Soviets were better at infiltration probably) orthogonal to bold public hits. The public hits are an intimidation tactic.
Edit: yes, I guess the US has similar optics in countries it operates killing drones as Russia has in Europe. Except probably worse.
https://truepublica.org.uk/united-kingdom/britains-secret-as...