Her body was found in a trash heap five days later.
The girl's murder ignited nationwide protests over allegations of government inaction, and a media campaign led to his arrest after years of him being on the loose.
"I am very thankful to the chief justice; he treated Zainab like his own daughter", Zainab's father Amin Ansari told Al Jazeera.
The Prosecutor General of Punjab province, Ihtesham Qadir said the man was also convicted of terrorism charges.
The girl's mother said, "We want that the suspect should be stoned to death for his crime as hanging in jail is a punishment which is given to other criminals but this beast deserves either public hanging or stoned to death". "Hanging him is just ordinary for him", Nusrat Amin told Al Jazeera.
Advocate Jamal also filed an application with the jail authorities, seeking permission to meet the suspect to consult him in private to access the need for the steps to be taken, including representation to defend him to ensure a fair trial. Imran was familiar with the victim's family and would also frequent her house. The perpetrator was found by police after he was seen on closed circuit television with Zainab.More news: Olympic streak over as Canada loses to Czechs in shootout
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Speaking to CNN last month, her family recalled a girl who loved mangoes and ice cream, and who wanted to be a doctor or a teacher.
Around 10 cases of child abuse are reported in Pakistan every day, according to Sahil, a child protection organisation.
In 2015, Kasur made headlines after a gang of pedophiles was busted who had abducted and sexually abused at least 280 children. Footage was created to use as blackmail against parents, according to the Human Rights Commission Pakistan.
Hundreds of local residents protested after Zainab's body was discovered, and two were killed when police fired shots to break up the crowd.