Five ethnic Chechens have gone on trial for the murder of Russian opposition politician Boris Nemtsov.
All say they are innocent. This is what we know about them so far.
Mr Dadayev was deputy commander of the North Battalion, a feared Chechen unit based in Grozny. According to state media, he resigned from his position on 28 February 2015 after a month's leave.
Boris Nemtsov was killed the previous day. Mr Dadayev's arrest became known a week later, on 7 March.
Mr Dadayev is the only suspect known to have confessed to Nemtsov's murder. But in an interview with a Moscow newspaper he says he made the confession so that a friend and junior officer who had also been detained could be freed.
Russia's human rights council said his confession was likely to have been extracted under torture.
Prosecutors say Mr Dadayev was the one who carried out the killing, and is described as the group's ringleader.
The North Battalion are part of the so-called Kadyrovtsy, militias that come under the command of the Chechen leader, Ramzan Kadyrov. Mr Kadyrov has written in defence of Zaur Dadayev, who he said was "sincerely devoted to Russia, ready to give his life for the motherland".
But he added that Mr Dadayev had been angered by French satirical magazine Charlie Hebdo's cartoons of the Prophet Muhammad. It has been suggested that the murder may have been a reprisal for comments that Boris Nemtsov made in support of Charlie Hebdo employees.
Nemtsov's friends are sceptical of this motive, since they say that Nemtsov was much better known for his criticism of President Putin than his support for the murdered cartoonists.
Anzor Gubashev is said to be the getaway driver. He, Mr Dadayev and a third suspect, Beslan Shabanov, fled the scene, abandoning their car before leaving for Chechnya, prosecutors say.
Despite having bruises on his wrists and legs after his arrest and initial interrogation, Gubashev said he had no complaints about his treatment at Lefortovo prison.
Shagid Gubashev is Zaur Dadayev's cousin and Anzor Gubashev's brother.
He has said that after he and brother Anzor heard of Mr Dadayev's arrest, they came to see him in Malgobek, a city in the republic of Ingushetia, bordering on Chechnya.
"Would we really have gone if we were in any way connected to any kind of crime?" Mr Gubashev asked Moskovsky Komsomolets. "It's illogical."
He says they were detained on the night of 6 March, adding that he and his brother were beaten and tortured by two men who referred to each other as Mikhailovich and Petrovich.
At first Mr Gubashev thought they might be drug enforcement officers, but they eventually demanded that he admit to killing Boris Nemtsov.
He says a bag was placed over his head and he was taken on an aeroplane. When the bag was removed he was in Moscow. The first time he saw his lawyer was in the court room on Sunday 9 March, he says.
Ramzan Bakhayev and Tamerlan Eskerkhanov
Little is known about these men. While the three other suspects were detained in Ingushetia, it is said that Mr Bakhayev and Mr Eskerkhanov were both arrested in Moscow.
Mr Eskerkhanov reportedly told a court that witnesses could confirm he was not at the scene of the crime when it occurred.
According to investigators the pair, along with Shagid Gubashev were not at the scene of the murder but are accused of illegally handling the weapon, and as accomplices in organising the crime.
Another man wanted in connection with the murder, Beslan Shabanov, reportedly killed himself when police tried to arrest him.
According to Interfax, the man was holed up in an apartment in Grozny when the incident occurred. He threw one grenade at officers before blowing himself up with a second.
Russian authorities are still seeking the arrest of Ruslan Mukhudinov, who is believed to have fled abroad.
Like Zaur Dadayev, Mr Mukhudinov served in the elite North Battalion. He is said to have ordered Nemtsov's killing.
But according to a lawyer for Nemtsov's family, the investigators have exaggerated Mr Mukhudinov's role and "the masterminds are high-ranking people".