Es gab schon mal eine Untersuchung zu Litvinenko; damals kommentierte sie der Guardian so:
"Six reasons you can't take the Litvinenko report seriously
....
While this analysis points to serious flaws in the report, it does not present evidence to exonerate Putin. As I said, I don’t know whether or not he is to blame. But what happened to the presumption of innocence and the need to build a case before declaring someone guilty?
It is clear that those who are behind these claims against the Russian president have an agenda, and are using a wealth of means in their attempts to convince others.
Key findings: who killed Alexander Litvinenko, how and why
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The public inquiry’s acceptance of so many of their questionable allegations casts a pall over Owen’s efforts and renders his report practically useless."
https://www.theguardian.com/world/2016/feb/05/litvinenko-report-get-it-wrong-putin
Der Autor, der auch 2 Bücher zum Thema geschrieben hat, begründet sein Urteil ausführlich.
Wenn es da keine neuen Erkenntnisse/Beweise (welche?) gibt, muß man zu demselben Schluß kommen.