Khartoum, Sudan (CNN) -- "Father we ask that you stand with your child Mariam. We ask that you strengthen and support her and grant her your grace."
It's the Sunday service in Khartoum and the pastor is leading the Christian congregation in prayers for Mariam Yahya Ibrahim, the mother of two convicted last month for the crime of apostasy after a court ruled that she abandoned the Muslim faith.
It's crime she strenuously denies, maintaining both that she was raised Christian -- in spite of being born to a Muslim father -- and that she would have been within her rights to leave the faith. Neither statement has won her clemency under Sudan's harsh interpretation of Islamic law.
As the pastor finishes his sermon, praying that God grant her strength, even "as the hangman's noose swings before her," he asks that the congregation pray that if she is not granted freedom, the Holy Father will grant her eternal life.
More than half the pews arranged before him are empty, and members of the choir struggle to fill the hall with their voices.
As Mariam's case has dragged on, Sudan's churches have begun to empty. We were asked to conceal the identity of the congregation; it is clear many Christians here are scared.
And activists tell us it is within good reason. After the secession of the majority Christian South in 2011, Sudanese President Omar al-Bashir announced this new Sudan would be Arab and Islamic in identity.
Although Sudan's constitution made provision for both ethnic diversity and religious freedom, shortly after the president's highly-publicized speech, the then-minister of religious affairs announced that no licenses would be granted to allow for the building of new churches.
Since South Sudan gained independence, problems between Khartoum and the mostly Christian regions bordering the new state have intensified.
The new edicts, many activists told us, felt highly politicized.
So how deep does the tolerance enshrined in the country's constitution actually run? Not very, says Nabeel Adeeb, a prominent Sudanese human rights lawyer, himself a Christian.
"If you look at the laws of the country," he tells us, "the laws favor Muslims."
"Number one, the crime of apostasy, which is creating a wall around Islam that nobody is allowed to leave."
And what is worse, he says, is the sense that extremist sentiment toward Christians is increasingly tolerated.
"In the war of propaganda between the two religions, Christianity will stand no chance. All the media is used to promote Islamic beliefs and to speak about Islam as the only religion and to insult other beliefs, especially Christianity which is normally referred to as being an infidel."
Last year, Adeeb says he documented around 200 cases of Christian foreigners deported for the crime of "evangelizing."
"It was almost en masse," he says. "They confiscated bibles and searched Christian centers. Deported them without instigating any legal procedures."
CNN has placed an interview request with Sudan's foreign ministry and has been promised that the foreign minister will address the concerns raised.
In the past, the Sudanese government has pointed to the many churches lining the streets of their capital as evidence of its tolerance. Many Sudanese we spoke to think the government is obsessed with a belief that -- as one put it -- "Christian missionaries (are) converting on every street corner." One Christian activist, who also declined to be identified, said: "The church is now contaminated with terror. You don't feel safe in prayer."
The only hope, she said, was that Mariam's trial had now brought that terror out into the international spotlight.