Pakistani Christian woman Asia Bibi's Tuesday appeal hearing on her death sentence for blasphemy was again cancelled - for the fifth time. No new hearing date has been set. Bibi's four previous hearings were also cancelled at the last minute by the court. Bibi, a mother of five, has been in prison since being sentenced to death for blasphemy in 2010. The accusation followed a heated dispute with Muslim colleagues. Blasphemy is a serious crime in Muslim-majority Pakistan and carries the death sentence, but human rights groups say the charges are often trumped up as a means of settling personal scores and vendettas. Anyone accused of blasphemy in Pakistan faces threats to their life from extremists. Relatives often have to go into hiding to escape the same fate, and being behind bars doesn't make the accused any safer. Sometimes extremists march into their prison cell and kill them while the guards turn a blind eye.