The defense is certain that the jury will not believe that the confession, that Zaur Dadayev made and later denied, was truthful, Kommersant says, citing a source close to the investigation.
Nemtsov, who was a high-profile Russian politician in the 1990s, was fatally shot in downtown Moscow on February 27.
There are five suspects in the case, including Dadayev, Tamerlan Eskerkhanov, Shagit Gubashev, Hamzat Bakhayev and Anzor Gubashev.
According to the Russian Investigative Committee, Dadayev has admitted his guilt and has given testimony against the other suspects. Later Dadayev claimed he was innocent, adding that he had an alibi.
According to Kommersant, additional evidence against Dadayev has since been found.
On Wednesday, the Moscow City Court ruled to extend the detention of Zaur Dadayev until April 28, while the investigation continues.