Slimane Bouhafs has been convicted of posting on social media saying 'Jesus overcomes the lies of Islam' with a picture of a jihadist killing a Christian.
Beth Fuller from Open Doors told Premier's News Hour these comments do not usually land people in jail, and it could be for another reason.
She said: "It's possible that actually the reason he's been targeted is because he's a member of a political separatist group that wants the region where he lives to be separate from the rest of Algeria.
"So it might be that this blasphemy charged has been trumped up, actually to silence him."
She went on: "The kind of comments he was making on Facebook are fairly common and don't usually lead to any repercussions, so the fact that he's been given this five-year prison sentence - which is actually the maximum sentence possible for blasphemy in the country - it's a surprise."
Population: 40.4 million, 39,000 Christians
Main Religion: Islam
World Watch List Rank: 37
Source of Persecution: Islamic extremism/ Dictatorial paranoia
The 49-year-old converted to Christianity in 1997 and is known for his commitment to religious freedom for all.
Open Doors told Premier his family are worried as Mr Bouhafs suffers from a medical condition which is worsened by stress, "his family and the Christian community there are certainly concerned for his well-being and his health," Beth Fuller said.
She told Premier the Christian community is working hard to help Mr Bouhafs: "The Protestant Church in Algeria are certainly working to try and see if there's anything that can be done to reduce this sentence. They're speaking out.
"It's very difficult for us to say what might happen. We can certainly hope and pray that actually this prison sentence is either overturned or reduced."
Listen to Premier's Antony Bushfield speak to Beth Fuller here: