If the Russians had wanted to kill him, they had ample opportunity to do so during the years when he was imprisoned or the eight years he lived in retirement in Salisbury.

https://consortiumnews.com/2018/03/13/the-strange-case-of-the-russian-spy-poisoning/

By James O’Neill

…Skripal was arrested in 2004. In 2006 he was convicted of treason and sentenced to 18 years imprisonment. In 2010 he was released as part of a prisoner exchange deal with Russian spies in U.S. jails. He went to live in the United Kingdom where he has lived in supposed retirement ever since. Another interesting fact, although again possibly coincidental, is that Salisbury, where Skripal lived, is only about 12 kilometres from Porton Down, the U.K.’s principal research centre for nerve agents. Read the rest of this entry »