Signal intelligence/ Intercepted electronic communications

American spies secretly intercepted communications between those involved in the murder of Alexander Litvinenko and provided the key evidence that he was killed in a Russian -backed “state execution,” The Telegraph can disclose.

The National Security Agency (NSA) obtained electronic communications between key individuals in London and Moscow from the time that the former spy was poisoned with radioactive material in central London. The evidence was passed to the British authorities.

A source familiar with the investigation confirmed the existence of American “intelligence material”. They said it would have been “inadmissible” in court, but that the British authorities were “confident that this was a state execution”.

Intercepted Communications Link Russia To Poisoning Death Of Ex-KGB Agent And Putin Critic