General Investigative Judge Imad Zein Monday recommended the death penalty for suspect Mark Yammine, who stands accused of killing two people in a coffee-related dispute in April.
Prosecutor-general Hisham Barakat was killed in a vehicle bomb attack on his convoy in eastern Cairo in June 2015.
The ruling is set to be sent to the Egyptian Mufti, an Islamic scholar and legal expert, although his opinion is non-binding.
The court will confirm the verdicts on July 22.
Hisham Barakat was killed in summer 2015 when his vehicle was blown up.
The 30 defendants were among a group of 67 people accused of involvement in the attack, the source said on condition of anonymity because he was unauthorized to speak to media.
Barakat was the highest-ranking state official to die in a militant attack since President Abdel Fattah al-Sisi, a former military chief, ousted President Mohamed Mursi, a Brotherhood leader, in 2013 after mass protests against his rule.
The group has also increasingly carried out attacks in Egypt targeting Christians in a spate of church bombings and shootings that have killed some 100 since December. The defendants were not only charged with assassinating Barakat, but multiple other charges were directed to them including espionage with the Palestinian movement of Hamas to incite instability in Egypt and belonging to an outlawed group.
Several local and global rights groups have condemned the increasing death sentences in Egypt. Critics claimed that the defendants undergo unfair trials and give testimonies under pressure.