Born in Saint Petersburg in the family of a physician.
In 1929–1936, he studied at the Leningrad State University at the Faculty of Soviet Law and at the Nikolay Krylenko Institute of Law, as well as (since 1939) in graduate school, which he did not complete due to the outbreak of the Great Patriotic War.
Since 1934 – Senior Investigator of the Leningrad Regional Prosecutor's Office.
In 1935–1938 – Senior Investigator of the Murmansk District Prosecutor's Office.
Since 1939 – Senior Investigator and Methodologist of the Leningrad City Prosecutor's Office.
On June 23, 1941, he was drafted into the army, served as a military investigator in the prosecutor's offices of the active armies and the Leningrad Front.
From September 1942 – in the Prosecutor's Office of the Soviet Union (investigator for the most important cases, prosecutor of the investigation department, prosecutor for special assignments under the Prosecutor General of the Soviet Union). He was engaged in investigating the crimes of the Nazis in the occupied territories of the Soviet Union.
Crimes against civilians, crimes against humanity committed by the Nazis in the occupied territories of the Soviet Union, Czechoslovakia, Poland, Yugoslavia, Greece;
In 1946, he was Deputy Prosecutor from the Soviet Union of Prosecutor Sergei Golunsky at the Tokyo International Trial on charges of the main Japanese war criminals (military aggression in the areas of Lake Khasan and the Khalkhin Gol River).
In 1957–1962 – Deputy Chairman of the Supreme Court of the Soviet Union.
In 1962–1972 – Chairman of the Supreme Court of the Russian Soviet Federative Socialist Republic. Conducted the trial of the participants in the Novocherkassk events, sentenced nine Novocherkassk workers to death.
He was a member of the International Commission of Inquiry to Expose the Atrocities of American Imperialism in Vietnam, a member of the United Nations Standing Advisory Committee of Experts on the Prevention of Crime and the Treatment of Criminals, a member of the Council of the International Organization of Democratic Lawyers, and an honorary doctorate in law from a number of foreign universities.
Smirnov's grave at the Novodevichy Cemetery in Moscow