Why use polonium on Novichok? [duplicate]
Litvinenko was allegedly poisoned by Russian operatives using polonium, Skripal and Navalny were allegedly poisoned by Russian operatives using Novichok. In all cases, the poison was traced to Russia very quickly.
It's a well known fact, that governments use radioactive paints for marking currency to trace cash transactions by following the radioactive trail. Russia is no exception. Furthermore, all radioactive materials that can be used for manufacturing nuclear weapons (i.e. polonium) are well documented, to the point that they can be traced to the mine they were extracted from. However, this does not mean that there is no way for operatives to retrieve samples of nuclear materials, mined by other countries (i.e. for UK to get some Russian polonium, or for Russia to get some US polonium).
When it comes to biochemical weapons, they have some signatures that can be traced to the regions they were manufactured in (impurities, particles of dust, aerosol microbes that accidentally find their way into the container containing the biochemical substance). Likewise, it's entirely possible to get samples of foreign biochemical weapons.
Furthermore, there are quite a few lethal chemicals, and less lethal chemicals which can be mixed to create a significantly lethal poison cocktail, which can be obtained off the shelf in any country.
I feel it is irrational to assume, that Russian operatives don't know these things - such operatives could only exist in movies, where the silly bad guy makes a mistake. So the question is - why use traceable polonium or Novichok, when you can use a poison that you buy or easily manufacture locally?