Gascón will hold a live news conference Thursday afternoon.
The Los Angeles County District Attorney's Office will announce Thursday afternoon whether it will recommend the resentencing of Lyle and Erik Menendez, who were sentenced to life without the possibility of parole in 1996 for the killings of Jose and Mary Louise "Kitty" Menendez.
District Attorney George Gascón had said his office would be reviewing the case to see whether the Menendez brothers' sentences could be shortened due to new evidence and a determination that the brothers are no threat to society.
The district attorney was scheduled to meet with reporters Friday afternoon to discuss the case of Erik Menendez, now 53, and Lyle Menendez, now 56, who remain behind bars at Richard J. Donovan Correctional Facility in San Diego.
The NBC4 I-Team confirmed the District Attorney's Office has filed a new 21-page document related to the Menendez case, which Gascón is expected to discuss during a live press conference Thursday afternoon.
A new piece of evidence the DA's office is reviewing involved a letter that Erik Menendez had written to a cousin about the sexual assault prior to committing the murders.
Gascón's office also said it's considering in a signed declaration by a member of the popular 1980s Puerto Rican boy band Menudo that he too was sexually assaulted by Jose Menendez.
The district attorney also said he would consider the early release of the brothers, who began serving their sentences at a young age.
The DA had said a hearing was scheduled for Nov. 29, but he said in an interview that he decided to speed up the process given the heightened public attention on the Menendez brothers' case, largely stemming from a Netflix series and social media movement.
A group of family members supporting the brothers also called earlier this month for the brothers to be released from state prison.
At an Oct. 16 news conference outside the downtown Los Angeles courthouse, Kitty Menendez's sister, Joan Andersen VanderMolen, said she struggled for many years to come to "terms with what happened in my sister's family."
Critics said Gascón is trying to leverage media attention through the national case ahead of the November election.
"LA County District Attorney George Gascón has once again demonstrated his opportunism," the Los Angeles Association of Deputy District Attorney said in a statement. "Throughout his disastrous tenure as DA, Gascón has consistently prioritized celebrity cases over the rights of crime victims, showing more interest in being in the spotlight than in upholding justice."
A September poll showed Gascon was trailing his challenger, Nathan Hochman, by 24 points.
Gascón said he is more open to "reviewing things that other prosecutors may not."
Also, the Beverly Hills Police Department, which was the investigating agency at the time of the murders, said it has not been contacted by the DA's Office regarding the new developments.