The family of Zeeshan ─ one of the victims of the Sahiwal encounter ─ became party on Thursday to a petition in the Lahore High Court seeking formation of a judicial commission to replace a joint investigation team probing the case.

The elite Punjab police had in an alleged fake encounter last month killed four people, including parents Khalil and Nabeela, their teenage daughter, and neighbour Zeeshan, sending shock waves across the country as one of the couple's three surviving children ─ who were witness to the episode ─ denied the official version in a video that went viral on social media.

The Punjab government has maintained since that Zeeshan was suspected of having links to Daesh, while the others were "collateral damage".

Read more: Punjab govt terms family's killing in Sahiwal encounter 'collateral damage'

A two-judge bench headed by LHC Chief Justice Sardar Mohammad Shamim Ahmed Khan told Zeeshan's heirs ─ whose appeal to become party to the petition was heard today ─ that the government, if it wished, could form a judicial commission under a district and sessions judge.

"It is not necessary that the application be from the victim's family," the bench informed the petitioners, when told that the victim's heirs were not the ones who had sent the federal government an application regarding the formation of a judicial commission.

The additional attorney general told the court that the federal government was waiting for a report on the case from the provincial government.

"You keep saying that a lot has been done [in the investigation], but no work has been done on paper," Justice Sadat Ali Khan complained.

After expressing its displeasure over slow progress in the case, the court ordered the police to record the statements of witnesses present at the site of the encounter.

"Police should record the statements of the people present at the scene of the crime," the judges ordered.

The court also directed the federal government to present its report regarding the formation of a judicial commission on February 14 and adjourned the case.

The Punjab government last week agreed to the formation of a judicial commission if the opposition was not satisfied with the JIT report on the Sahiwal tragedy.

On Feb 3, Prime Minister Imran Khan in a one-on-one meeting with Punjab Chief Minister Usman Buzdar, directed him to ensure speedy justice to the grieving family.