When Patrick Ball was introduced to Ibero’s database, the director of research at the Human Rights Data Analysis Group in San Francisco, California, saw an opportunity to turn the data into a predictive model. Ball, who has used similar models to document human rights violations from Syria to Guatemala, soon invited Data Cívica, a Mexico City–based nonprofit that creates tools for analyzing data, to join the project.

Ball analyzed the data reporters had collected from a variety of sources – including on-the-ground interviews, police records, and human rights groups – and used a statistical technique called multiple systems estimation to roughly calculate the number of unreported deaths in three areas of the capital city Manila.

The team discovered that the number of drug-related killings was much higher than police had reported. The journalists, who published their findings last month in The Atlantic, documented 2,320 drug-linked killings over an 18-month period, approximately 1,400 more than the official number. Ball’s statistical analysis, which estimated the number of killings the reporters hadn’t heard about, found that close to 3,000 people could have been killed – more than three times the police figure.

Ball said there are both moral and technical reasons for making sure everyone who has been killed in mass violence is counted.

“The moral reason is because everyone who has been murdered should be remembered,” he said. “A terrible thing happened to them and we have an obligation as a society to justice and to dignity to remember them.”

Patrick Ball, director of research at the Human Rights Data Analysis Group, and a statistician who has conducted similar estimates of violent deaths in conflicts in other regions, said the study was strong and well reasoned. But he cautioned that the authors may have underestimated the amount of uncertainty caused by the ongoing conflict.

The authors used different variations of mathematical models in their calculations, but Dr. Ball said that rather than presenting a single figure — 64,260 deaths — as the estimate, it may have been more appropriate to present the number of deaths as a range from 47,457 to 88,332 deaths, a span that encompasses all of the estimates produced by modeling the overlap among the three lists.

“It’s really hard to do this kind of thing in the middle of a conflict,” Dr. Ball said. “It takes time, and it takes access. I think you could say the range is larger, and that would be plausible.”

Kristian Lum: “The historical over-policing of minority communities has led to a disproportionate number of crimes being recorded by the police in those locations. Historical over-policing is then passed through the algorithm to justify the over-policing of those communities.”

“If you’re not careful, you risk automating the exact same biases these programs are supposed to eliminate,” says Kristian Lum, the lead statistician at the San Francisco-based, non-profit Human Rights Data Analysis Group (HRDAG). Last year, Lum and a co-author showed that PredPol, a program for police departments that predicts hotspots where future crime might occur, could potentially get stuck in a feedback loop of over-policing majority black and brown neighbourhoods. The program was “learning” from previous crime reports. For Samuel Sinyangwe, a justice activist and policy researcher, this kind of approach is “especially nefarious” because police can say: “We’re not being biased, we’re just doing what the math tells us.” And the public perception might be that the algorithms are impartial.

The Human Rights Data Analysis Group, an independent scientific human rights organization based in San Francisco, has counted at least 17,723 people killed in Syrian custody from 2011 to 2015 — around 300 every week — almost certainly a vast undercount, it says.