Prosecutors claimed Rabee Khalifa had been stationed outside a church as an armed guard when he killed Imad Kamal Sadeq and his son during an arguement last December in Minya province.
The deaths of Mr Sadeq, 49, and his 21-year-old son prompted the country's beleagered Coptic Christian population to protest and demand greater protection from the state.
Speaking last year, the head of the local diocese, Archbishop Macarius, who led prayers at the funerals of the two men, demanded a response from authorities.
He said: "We call for all armed police officers assigned to guard churches to be checked.
"Are they qualified to carry live ammunition, so that they don't become a source of danger rather than protection."
According to the Reuters news agency, the death sentence issued on Tuesday is subject to appeal.
Security has been boosted at churches and monasteries across Egypt in recent years following a spate of deadly attacks targeting believers.
Twin suicide blasts (pictured) at Coptic churches in Alexandria and Tanta on Palm Sunday in 2017 left at least 45 died. Islamic State claimed responsibility.
Twenty-five people were killed in an explosion at a chapel near the Coptic Orthodox Cathedral of St Mark in Cairo on 11th December 2016.
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