A member of the parliament's lower house and the only woman to run for the Russian presidency in the 1996 election, Starovoitova, 52, was shot dead in the stairwell of her home in central St. Petersburg, Russia's second city, in November 1998.
The jury decided that the lawmaker was slain but said the murder was not politically motivated. Starovoitova, leader of Democratic Russia party, mulled joining the presidential race in 2000.
The defendants, Vyacheslav Lelyavin and Pavel Stekhnovsky, had been accused of helping organize the assassination.
Lelyavin was found guilty on all counts. He was detained in 2004 and faced charges of tapping telephone conversations and attempted murder of a state or public figure.
Stekhnovsky was found guilty only of obtaining a weapon and cleared of murder charges. Stekhnovsky was arrested in Belgium in 2004 and extradited to Russia where he was accused of involvement in obtaining weapons, attempted murder of a state or public figure and a terrorist attack.
Two people, intelligence officer Yury Kolchin and Vitaly Akishin, were sentenced in July 2005 to 20 and 23.5 years in jail, respectively, for organizing the murder and gunning down Starovoitova.
Starovoitova served as an ethnic advisor for President Boris Yeltsin in the early 1990s, was a human rights champion, worked with prominent human rights advocate and democracy promoter Andrei Sakharov, and was known as an uncompromising politician.