Testimony will begin on Wednesday in the trial of Daniel Maoz, who is charged with killing his parents in their Jerusalem home last year, and his siblings are slated to be key witnesses for the prosecution.

The bodies of Noah and Nurit Maoz were found in the living room of their home in the capital's Ramot neighborhood. Two weeks later, their son Daniel, 28, was arrested as the main suspect in their murders; police believe he killed them to get his inheritance.

His lawyer, David Barhoom, told the Jerusalem District Court that his client denies the charges against him.

Although members of the Maoz family have refrained from speaking to the media about the case, Haaretz has obtained documents from the case file indicating that the day the couple's bodies were found, Daniel Maoz's siblings began to suspect he was responsible for their parents' deaths. In her initial statement to the police, the defendant's 34-year-old sister, Tamar, volunteered the information that Daniel had a gambling problem.

"My father discovered it about seven or eight years ago," she said in her statement. "Since then, there were three or four episodes in which Daniel was forced to ask my parents for financial help because he got involved in gambling and had to pay people money ... They lent him about NIS 400,000 to NIS 500,000 in all."

She also said that to repay the debt, he had opened a joint account with his mother into which his salary was paid. He did not have the right to make withdrawals from this account.

"He was living on the minimum possible," Tamar added.

She also said Daniel was not on good terms with his siblings, meaning Tamar herself and Daniel's twin brother, Nir.

Tamar Maoz is expected to be the first witness at trial, to be followed by her brother Nir, who reportedly found his parents' bodies lying in pools of blood in their living room.