The alleged mastermind of the killing, Erzhan Utembaev, the former head of the Senate administration, "categorically" denied the charges, according to his wife Lyudmila Ten.
Ten also said that another chief defendant, Rustam Ibragimov, denied the charges laid against him. Prosecutors believe Ibragimov killed Sarsenbaev.
Several former security officers are among the defendants.
The trial is being held in Taldy-Qorgan, some 250 kilometers north of the country's commercial capital, Almaty.
Sarsenbaev's relatives asked the court to hold its hearings in Almaty to enable relatives to attend the trial.
Sarsenbaev, a leader of the opposition party Naghyz Ak Zhol, was found dead near Almaty in February along with his driver and his bodyguard.
Sarsenbaev lived in Almaty until he was kidnapped and was apparently murdered in the Taldy-Qorgan region.
The trial was adjourned until June 19.
Kazakhstan's Fallen Opposition
February 13, 2006: Altynbek Sarsenbaev -- a leader of the Kazakh opposition, co-chairman of the Naghyz Aq Zhol party, former minister of information, former Kazakh ambassador to Russia, former secretary of Kazakhstan's Security Council -- is found dead with his bodyguard and his driver, shot to death, execution style, with their hands bound behind their backs.
November 11, 2005: Zamanbek Nurkadilov-- prominent Kazakh politician, former mayor of Almaty, former Minister of Extraordinary Situations, and since a vocal critic of President Nursultan Nazarbaev since March 2004 -- is found shot to death, with two shots in his chest and one in his head. Kazakh authorities officially rule the case a suicide.
June 2, 2005: Batyrkhan Darimbet -- opposition journalist and editor in chief of the weekly AZAT -- is killed in what is officially reported as a traffic accident. Relatives and activists assert that it was a political killing.
December 19, 2004: Erzhan Tatishev -- head of Kazakhstan's largest bank, TuranAlemBank -- is killed in what was officially described as a hunting accident. Kazakh political observers allege that it was a premeditated assassination.
July 20, 2004: Askhat Sharipzhan-- independent journalist and political commentator for NAVI online -- dies of injuries sustained several days earlier in what was officially reported as a hit-and-run accident. Relatives and colleagues believe it was an assassination.
November17, 2002: Independent journalist Nuri Muftakh is killed in what is officially reported as a traffic accident. Colleagues and activists regard the death as suspicious.
January 4, 2002: Human rights activist Aleksei Pugaev is found dead, the victim of a hit-and-run car accident. Colleagues regard the circumstances as suspicious and no one is ever arrested in connection with the death.
(compiled by RFE/RL's Kazakh Service)
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