Pakistan's Supreme Court is to rule on whether a government amnesty lifting corruption charges against former PM Benazir Bhutto is legal.
Ms Bhutto is due to arrive in Pakistan on 18 October
The amnesty was one of Ms Bhutto's conditions for her return to Pakistan next Thursday ahead of a possible power sharing deal with President Musharraf.
Gen Musharraf won another term in office in presidential elections held last Saturday.
That election is also being challenged in the Supreme Court.
The court's Chief Justice, Iftikhar Chaudhry, said he would hear five petitions against the amnesty, known as the National Reconciliation Ordinance.
He said the court would rule on whether the "ordinance and its provisions are beyond the constitution".
Chief Justice Chaudhry said anyone granted an amnesty under the ordinance would "not be entitled to claim any protection if this court concludes that the ordinance and its provisions are beyond the constitution," the AFP news agency reports.
It is not due to start detailed work on the case for another three weeks.
The petitions were put forward by a leading Islamic politician, Qazi Hussain Ahmed, and four other individuals.
Friday's decision opens the possibility of the court both declaring that Gen Musharraf cannot continue to be president and also of Benazir Bhutto facing trial in cases dating back nearly 20 years.
Ms Bhutto has declared that she will fly into Karachi on Thursday. She leads the country's biggest party, the Pakistan People's Party.
She and President Musharraf have been in prolonged negotiations about a power sharing arrangement.
Gen Musharraf has been under pressure from Washington to reach a deal as the US has become increasingly concerned at his growing unpopularity in Pakistan.
On Wednesday he asked Ms Bhutto not to return from her self-imposed exile until his re-election had been endorsed by the Supreme Court.
However, her advisers said she would ignore the request. Gen Musharraf made clear in a BBC interview on Friday that he would not prevent Ms Bhutto from returning.