A Muslim policeman also died when three gunmen in a car raked worshippers emerging from mass with bullets in Nagaa Hammadi, near the southern town of Qena.
Mohammed Ahmad Hossein, also known as Hamam Kammouni, was considered the ringleader of the attack.
A Qena court said it would also announce verdicts against the two other Muslim suspects, Qorshi Abul Haggag and Hendawi Sayyed, on February 20. All three had pleaded innocent to charges of carrying out the January 6, 2010 attack.
The chief judge of the Qena security court, which allows no right of appeal, gave no motive for the attack in which the Copts were gunned down.
Threatening to exacerbate tensions between Muslims and Egypt’s minority Christians, a suicide bomber killed 21 people outside a church in the northern city of Alexandria after a New Year’s Eve mass at the start of 2011.
At the time, the Nagaa Hammadi attack was the deadliest of its kind since 2000 when 20 Copts were killed in sectarian clashes.
Coptic Bishop Anba Kirolos of Nagaa Hammadi welcomed the ruling and said his flock were “satisfied,” but a defence lawyer, Alaa Abu Zeid, said it was influenced by the widespread outrage over the Alexandria bombing.
A Qena prosecutor charged the three suspects arrested two days after the attack with “premeditated murder, putting the lives of citizens in danger, and damage to public and private property.”
The killings near Qena sparked outrage among Egypt’s Copts and led to clashes with police. International condemnation poured in, with the United States protesting at “an atmosphere of intolerance” in Egypt.
Egyptian officials denied a sectarian element in the attack, insisting it was a purely criminal act and linking it to the alleged rape of a Muslim girl by a Coptic man.
The unclaimed Alexandria bombing against the Copts, who mark Christmas on January 7, led to a diplomatic rift between the Vatican and Cairo, which earlier this month recalled its envoy to the Holy See.
Egypt said the envoy was recalled in protest at remarks by Pope Benedict XVI condemning the attack in the Mediterranean city.
The head of the Roman Catholic Church has expressed his solidarity with the Copts and called on world leaders to protect them in the aftermath of the church bombing.
The attack was “yet another sign of the urgent need for the governments of the region to adopt … effective measures for the protection of religious minorities,” the pope said.
The comments were part of a strongly worded defence of the rights of Christians living in Muslim majority countries.
On New Year’s Day, just the hours after the attack, the pope called for an end to the “discrimination, abuse and religious intolerance which are today striking Christians in particular.”
Copts make up about 10 percent of Egypt’s 80-million population