Polonium leaves a trail. Feds would investigate this.
I understand it’s ridiculously expensive due to rarity.
There was a thread a month ago on the guy who figured out what got Litvemenko.
Yes.
Litvinenko's doctors didn't figure out what was wrong with him until shortly before he died. But, when polonium was identified as the cause, Scotland Yard tracked the trail all over London and across Europe back to Mother Russia.