Shafqat Emmanuel Masih, 46, and his wife Shagufta Kausar, 43, are both jailed awaiting capital punishment after Muslim complainants claimed Shafqat sent them text messages blaspheming the Prophet Muhammad in 2013.
Mr Masih denies ever sending the messages, and has said he only confessed to the crime because the police tortured him and then threatened to torture his wife as well.
The couple have four children and worked at St John's School in Gojra, eastern Pakistan, before their arrest.
Shafqat Masih is paralysed from the waist down, and has applied for bail complaining of bedsores and a significant deterioration of his health.
He told the Christians in Pakistan website: "There is no man who can stand to see his wife being tortured by police, so to save my wife, I confessed."
He also said in an online petition calling for his freedom and legal support: "I have developed bedsores and I may die in jail as there is no possibility of a better treatment there."
World Vision in Progress, an advocacy organisation defending the couple, said: "There was no evidence that the text messages came from a phone owned by the couple.
"In the first place they had lost the phone some months before July 2013 and secondly there was no SIM card in their names.
"The only evidence police produced was a bill for a SIM card from a shop owner which is unheard of."
Pakistan's blasphemy laws are often used by Muslims to target Christians and other minorities.
While no one has ever been killed under the laws, many Christians are on death row because of them.
A high profile case is that of Asia Bibi, who has been on death row for more than five years because of blasphemy allegations which she denies.
The couple have appealed their death sentence and a hearing will be held in the High Court on March 5th 2016.
