The quoted cause of a Christian's death in prison is heart attack and it may be real but the prospect of spending his rest of life in prison and occasional bouts of violence in prison cell from pious Muslims, security guards or other criminals, is the one that made him dead long back. The report says he was accused of blasphemy by business rival in the year 2006 and subsequently sentenced to life imprisonment last year.
In Islamic Pakistan, all it takes is a rumor or an allegation to put lives of Christians in danger; conviction in courts is not needed as in some cases the accused have been shot dead by pious Muslims even after they were found non guilty (here, here, very recent case); this constant threat, in addition to official discrimination and persecution, must be keeping Christian community under tremendous pressure and some simply seek conversion to Islam as an escape route out of this as it was found out recently.
Karachi: Christian jailed for blasphemy dies in suspicious circumstances, say activists. (or as reported in guardian,uk)
Qamar David, a Christian originally from Lahore Pakistan, but living in Karachi died in prison while serving a life sentence for blasphemy. Official sources confirm that the man died last night in his cell, after a heart attack. in the past he had suffered several episodes of violence within the prison walls. Human rights activists are calling for an investigation to ascertain the "true causes" of death....
Qamar David was a native of Hamza, near Lahore (Punjab), but was a self employed painter in Karachi in the south of the country. On 8 June 2006 he was reported by a business rival on false charges of blasphemy in accordance with Articles 295 and C of the Pakistan Penal Code. According to the plaintiff, he sent telephone messages with insulting words against Muhammad.
....On 25 February 2010, the Karachi court adjunct Judge Jangu Khan, found him guilty of "outrageous" words against Muhammad, and exclusively based on the "black law" and the testimony of his accuser, David Qamar was sentenced to prison for life.....For conviction, all that is needed is word of accuser! No wonder then that many Non Muslims fall prey to this law. This offers very convenient means for Muslims to settle scores with their rivals in profession of other faiths. The way this law works shows how precarious the lives of Non Muslims will be Islamic society when Sharia is under implementation.
Note: Kidnapping of Christian (Hindu women also) women and girls is a regular practice in Pakistan. One recent report on this kind: Captors tried to force a Christian mother of seven to convert to Islam.
Another report from asianews.com which was mentioned previously in my blog (here): Pakistani Christians convert to Islam because of threats and intimidations.