Seven-year-old Zainab’s rape and murder has remained in the limelight ever since images of the child’s body abandoned in a heap of trash started circulating on social media earlier this year.
What led the police to the suspect, identified as Imran Ali, a relative of the child, was a technique involving the most basic element in human cells, widely known as the deoxyribonucleic acid (DNA), that carries all our individual genetic information.
In 2015, Kasur district had first made it to headlines across the country and abroad for scores of cases of child sexual abuse reported from its Hussain Khanwala village. Later that year, a joint investigation team was looking into reports of a network producing and circulating child pornography, involving forced sexual acts with children, when the first in the series of 12 cases that ended with Imran Ali’s arrest was reported.
The provincial administration was quick to get the newly formed Punjab Forensic Science Agency (PFSA) involved, sending samples collected from the crime scene to the lab for DNA examination.
First used in a criminal investigation anywhere in the world as far back as 1986 – to track down a suspect in two rape cases three years apart in Leicester, United Kingdom – DNA examination of various pieces of evidence including clothes worn by the victim, identified as Asma Bibi, at the time of the kidnapping enabled the agency to prepare a profile of the suspect.
“In cases of sexual assault, the agency examines evidence for body fluids like semen, blood, saliva, and sweat, and prepares a DNA profile which is the gold standard of evidence everywhere in the world,” Dr Ashraf Tahir, the PFSA director general, tells MIT Technology Review Pakistan.
Soon the police started bringing suspects to the PFSA headquarter in Lahore for DNA profile matching, but none of them corresponded to the profile prepared based on samples made available to the agency.
In May 2016, the agency was again approached by the Police Department. This time, it wasn’t about profiling of more suspects, instead they brought another case from Kasur, involving assault and killing of a child named Tehmina.
During forensic analysis, PFSA scientists found that the DNA profiles of the culprit involved in Asma’s and Tehmina’s cases were identical, Dr Tahir recalls.
“That’s when we told the police that they were looking for a serial killer,” he says, adding that a number of suspects were subsequently brought in for DNA profiling. “It would be unfair to say that enough effort was not put in by law enforcers. They brought at least 71 suspects in the two cases but DNA profiles did not match in any of those instances,” the director general remarks.
Come 2017, the frequency of cases reported from Kasur escalated. A series of cases were brought to the agency in January, February, July, and November. Zainab’s case was the first to be brought in 2018, and soon enough it became the tipping point that would jolt the conscience of the entire nation. As Kasur saw unprecedented public anger with riots breaking out against what the residents believed was the complacency of the administration, social media platforms also became sites of protest and catharsis as #JusticeforZainab trended on Twitter for multiple days in major cities across the country.
The administration kept working at the backend all this while. The initial observation about the involvement of a serial criminal had been further ascertained by then, as DNA profiles prepared in all the cases reported from the district, including Zainab’s, were found identical.
Investigations also showed that all 12 cases had occured in a 2.5-kilometer radius.
Police were bringing new suspects to the PFSA lab everyday for DNA profiling, but without any luck.
“I decided to approach Maj (retd) Azam Suleman Additional Chief Secretary and Arif Nawaz Inspector General of Police, and suggest a different tactic. Instead of picking up some people on the basis of suspicion, I proposed that we should prepare DNA profiles for the entire male population in the target age group, and go by the elimination route to catch the culprit,” the PFSA director general says.
He says computer forensic and audio-visual analysis of the footage obtained from the closed circuit television (CCTV) camera had already confirmed that the suspect was between 20 and 40 years of age.
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“It was unlike anything we had done in the past so we declared an emergency in the agency and geared up for round the clock operations instead of the single-shift routine,” he says, adding that once the government approved the plan, special teams were formed to collect oral swabs of the target male population of the area.
The agency also obtained population census data from the federal government to avoid any misinformation. The PFSA teams continued a door-to-door campaign to collect oral swabs for six consecutive days, collecting 1,187 samples. Teams at the lab examined 813 samples before arriving at the match. The 814th sample was that of Imran Ali, a relative of Zainab, and it matched with profiles prepared in all 12 instances.
Once Imran Ali’s DNA profile was matched, the agency asked the police to bring him again for reconfirmation of the DNA profile. The police brought the prime suspect again, along with a few other suspects to avoid leakage of information. “We did his DNA profile again and it was confirmed without an iota of doubt that he was the culprit. Later, he admitted to his crimes but we proceeded to verify his statement with a polygraph test. In fact, we also wanted to test the accurately of our polygraph equipment,” Dr Tahir maintains.
The polygraph test was spot on. With the DNA samples and polygraph result, the case was set to be sent for trial.
To a question about the state of the infrastructure available at the lab, the PFSA director general says that the facilities are comparable to leading forensic labs across the globe. “We have received praise from some internationally acclaimed forensic experts for solving the case in a short span of time. Identification of body fluids like semen, blood, saliva, and sweat and preparation of DNA profiles would have been a time-consuming task in the absence of latest technology,” he says.
“DNA is a chemical compound available in all living cells. It is the blueprint of life that carries genetic instructions used in development, functioning, and reproduction of all known living organisms,” he says, “We conduct a Short Tandem Repeat (STR) analysis to distinguish one DNA sample from another. The PFSA is equipped with facilities to conduct DNA quantification and xeroxing (copying) because generally we find very small samples on raw evidence.”
Dr Tahir says that the agency has the technology to make 800 million copies of DNA in around three hours. So far, it has prepared a DNA database of over 12,000 criminals, the biggest and the most authentic collection of DNA profiles available in Pakistan, he adds.
Ahmad Raza is a journalist based in Lahore.