Born in Mogilev to a Ukrainian family, Krestinsky studied law at Saint Petersburg Imperial University, where he embraced revolutionary politics.

After the 1917 February Revolution brought an end to the monarchy, Krestinsky led the Bolsheviks in Yekaterinburg before returning to Petrograd.

With the rise of Joseph Stalin, Krestinsky gradually fell from power and lost his positions in the government, save for his post as Soviet ambassador to Germany.

[5] In March 1921, after the early death of Yakov Sverdlov, Krestinsky received a sudden promotion to the post of Secretary of the Central Committee.

In April 1928, he publicly repudiated the opposition, claiming that he had never been an active member, making him one of the first Trotskyists to capitulate to Stalin.

In March 1937, early in the Great Purge, Krestinsky was suddenly transferred to the post of USSR Deputy People's Commissar for Justice.

[11]The following day, he made a total reversal of his position: Yesterday, under the influence of a momentary keen feeling of false shame, evoked by the atmosphere of the dock and the painful impression created by the public reading of the indictment, which was aggravated by my poor health, I could not bring myself to tell the truth, I could not bring myself to say that I was guilty.

[13] He went on to 'confess' that he was a German agent, and that he had met Trotsky in the Tyrol resort of Merano in October 1933 to receive instructions on sabotage.

However, Trotsky was under constant surveillance by Soviet agents at the time and KGB records from the 1950s do not mention any trip to Merano.

[14] He was partially exonerated during Nikita Khrushchev's destalinisation program, when, on 27 October 1963, Izvestia carried an article by the former soviet ambassador to Great Britain, Ivan Maisky, praising Krestinsky as a "diplomat of the Leninist school.".

[16] Joseph E. Davies, who was the US Ambassador to the USSR in 1938, described Krestinsky in his memoir, Mission to Moscow as "a short-sighted little man with a rather repulsive face" – but his view must have been coloured by the fact that he accepted the confessions by defendants at the March 1938 show trial, which he attended.

He told the US State Department that "if the charges are true a terrible sordid picture of human nature at its worst is being unfolded.

He was astoundingly myopic, so that his shrewd eyes, hidden behind lenses a quarter of an inch thick, seemed to have a timid expression.

[19] Their 19-year-old daughter, Natalya, a student at a Medical Institute in Moscow, was arrested in June 1939 and exiled to Krasnoyarsk territory for three years.