An Egyptian appeals court on Tuesday quashed one of two life sentences handed down to Mohammed Morsi since his 2013 overthrow, in the Islamist ex-presidents second appeals victory in a week.
Morsi's lawyer and a judicial source confirmed the verdict from the Court of Cassation, Egypt's highest judicial authority.
The court ordered a retrial in the case, Morsi's lawyer Abdel Moneim Abdel Maqsoud told AFP, adding: "The verdict was full of legal flaws."
The ruling also quashed the sentences against several Muslim Brotherhood officials who stood trial alongside Morsi on charges of spying for Iran and Palestinian militant group Hamas, Abdel Maqsoud said.
The decision was the latest legal victory for the 65-year-old, who has been convicted and sentenced in all cases against him since being removed from office in 2013.
But his year in power proved deeply divisive and he was overthrown by then-army chief and now President Abdel Fattah al-Sisi following mass street protests.
A crackdown on Morsi's Muslim Brotherhood followed, with the movement blacklisted, hundreds of its supporters killed and thousands jailed or sentenced to death.
The courts' handling of the cases against Morsi and his supporters, many of whom have been convicted after mass trials lasting just days, has drawn criticism from Western governments, human rights groups and the United Nations, which described the trials as "unprecedented" in recent history.
Last week, the Court of Cassation also overturned a death sentence handed down against Morsi on charges of taking part in prison breaks and violence against policemen during the 2011 uprising against Mubarak.
The decision enabled Morsi to stop wearing the red uniform reserved for death row prisoners.
Five co-defendants, including Brotherhood supreme guide Mohamed Badie, who also received death sentences, are to be retried too in that case.
New appeal next week
From next Monday, the court is to start reviewing a second life sentence handed down against Morsi in a separate trial on charges of stealing documents relating to national security and handing them over to Qatar, a longstanding supporter of the Brotherhood.
Last month, it upheld a 20-year jail sentence handed down against Morsi on charges of ordering the use of deadly force against protesters during his year in power.
Morsi is being held at the Borg el-Arab prison near the northern city of Alexandria.
A veteran activist and engineering professor, Morsi emerged as a compromise candidate for the Brotherhood to field in Egypt's first democratic presidential election in 2012.
He narrowly won the vote but was soon accused of failing to represent all Egyptians and of trampling the ideals of the anti-Mubarak uprising.
His rule was marked by deep divisions in Egyptian society, a crippling economic crisis and often-deadly opposition protests.
Morsi was removed by Sisi on July 3, 2013 after millions took to the streets demanding his resignation. Sisi became president a year later.
Morsi denounced a "coup" and his supporters insisted he was still the legitimate president.
Hundreds were killed in clashes that erupted when security forces dispersed two pro-Morsi protest camps in Cairo in August 2013.
The years following Morsi's overthrow saw a surge in bombings and shootings targeting security forces, particularly in the northern Sinai Peninsula, a stronghold of the Islamic State group.
The jihadists say the attacks are in retaliation for the crackdown on Islamists.