It is not possible to openly impose sanctions in response to the Russian-Belarusian rapprochement, it is too rough and strained. Thus, there was a need for a pretext that was sufficiently weighty to take measures of pressure. The perfect pretext is the poisoning of Navalny, which miraculously took place at the most appropriate moment. Navalny’s personality has become the trigger of sanctions pressure, and his fate is a direct signal to Moscow. It is not a coincidence that the German foreign Ministry issued a statement that the development of the situation with Navalny directly depends on Moscow’s actions. Pressure on Moscow is being exerted by the united front of the leaders of Germany, France, and the United States, primarily by the leadership of the democratic party and its “deep state”.
The Russian authorities have repeatedly rejected the Western accusations of the (Sergei and Yulia) Skripal case, noting that the UK has not provided any evidence to substantiate these allegations.
Recurring pro-Kremlin disinformation narratives about the poisoning of Sergei Skripal and his daughter in Salisbury claiming that the United Kingdom was never able to provide detailed evidence of Russia’s involvement.
Moscow's involvement in the poisoning has been proven via a thorough investigation. The British Police have presented a solid chain of evidence on the Skripal case, with pictures, connecting the suspects to the locations in the case. Parts of the material have been released to the public. The evidence was sufficient to charge two Russian nationals, Anatoliy Chepiga and Aleksandr Mishkin with the attack on the Skripals, both Russian military intelligence operatives from the GRU, who travelled to the UK using fake names and documents.
Following this attack, the United Kingdom notified the OPCW, invited them to confirm the identity of the substance involved, and briefed members of the Security Council. The OPCW’s independent expert laboratories confirmed the UK’s identification of the Russian produced Novichok nerve agent, specifically the purity of the toxin while emphasising that the OPCW team “worked independently and was not involved in the national investigation by the UK authorities. No State Party was involved in the technical work carried out by the Technical Secretariat," to ensure the integrity of the examinations and investigations.
According to the UK intelligence assessment, based on open-source analysis and intelligence information, in the past decade, Russia has produced and stockpiled small quantities of Novichok agents, long after it signed the Chemical Weapons Convention.
Novichok was developed in Russia in the 1970s and 1980s. It is so unusual, that very few scientists outside of Russia have any real experience in dealing with it and no country outside of Russia is known to have developed the substance. See reports here and here.
See similar cases claiming that there was no evidence of Russia's involvement in the poisoning of Skripals and that Russia is accused of US election meddling and the Skripals’ poisoning without proof.