General Pervez Musharraf considered changing the law

The 18-year-old was among those who signed a petition accusing Dr Sheikh of making blasphemous remarks during a class in October.

A local mullah filed a criminal complaint based on the boy's accounts and Dr Sheikh has been in prison ever since.

He says the case was motivated by those who don't like his political views on controversial subjects such as Kashmir.

Speaking before the court hearing, Dr Sheikh said he couldn't conceive of saying anything blasphemous; he said he had discussed aspects of the prophet Mohammed's life during classes, but that his words had been twisted.

However, the chief complainant, who took up the case on the students' behalf, said any Muslim would rather shoot himself than make false allegations.

The prosecuting lawyer said as there was no antagonism between the teacher and his students, there had to be some cause behind the original complaint.

Human rights criticism

Human rights groups have called for a change in the blasphemy laws, which stipulate a mandatory death sentence for anyone found guilty, although no one has been executed to date.

It's estimated that hundreds of people are currently being detained on blasphemy charges, and minority religious groups complain the law is used to persecute them.

Under the current system, if someone is accused of blasphemy, the police have to make an arrest without investigation.

Last year, the government tried to introduce a procedural change, which would mean an inquiry would precede any arrest.

But it stepped back from doing so after pressure from hardline religious groups.