alexander litvinenko
A counterterrorism unit has taken over the case. Sergei Skripal remains in critical condition.
Sergei Skripal and his daughter are in critical condition at an English hospital.
Former agent-turned-Kremlin critic Alexander Litvinenko died after drinking tea laced with radioactive poison in 2006.
WHAT'S HAPPENING
"If the Russian state is responsible, Putin is responsible."