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Predictive Policing Reinforces Police Bias

Issues surrounding policing in the United States are at the forefront of our national attention. Among these is the use of “predictive policing,” which is the application of statistical or machine learning models to police data, with the goal of predicting where or by whom crime will be committed in the future. Today Significance magazine published an article on this topic that I co-authored with William Isaac. Significance has kindly made this article open access (free!) for all of October. In the article we demonstrate the mechanism by which the use of predictive policing software may amplify the biases that already pervade our criminal ...

Reflections: It Began In Bogotá

It was July of 2006, I’d spent five years working at a local human rights NGO in Bogotá, and I had reached retirement age. But then a whole new world opened up for me to discover. Tamy Guberek, then HRDAG Latin America coordinator, whom I had met at the NGO, approached me about becoming part of the HRDAG Colombia team as a research/administrative assistant. Over a cup of suitably Colombian coffee, the deal was quickly "signed.” My responsibilities ranged from fundraising to translations, from support in data gathering for estimates on homicides and disappearances in various regions of Colombia to editorial support to different Benetech-HRDAG ...

Guatemala’s Bol de la Cruz Found Guilty

Today Guatemala’s former national police chief Colonel Héctor Rafael Bol de la Cruz was convicted and sentenced to 40 years in prison for his role in the 1984 kidnapping and disappearance of 27-year-old student union leader Fernando Garcia, who was last seen when officers detained him outside his home. Along with Bol de la Cruz, former senior police officer Jorge Gomez was also tried; he received a sentence of 40 years in prison. That verdict comes in part because of testimony this month by HRDAG’s Patrick Ball, who served as an expert witness and presented data analysis done with colleague Daniel Guzmán to assess the flow of thousands of ...

Update on Work in Guatemala and the AHPN

HRDAG has sampled and analyzed documents at Guatemala's AHPN and has testified against war criminals based on that analysis.

Data ‘hashing’ improves estimate of the number of victims in databases

But while HRDAG’s estimate relied on the painstaking efforts of human workers to carefully weed out potential duplicate records, hashing with statistical estimation proved to be faster, easier and less expensive. The researchers said hashing also had the important advantage of a sharp confidence interval: The range of error is plus or minus 1,772, or less than 1 percent of the total number of victims.

“The big win from this method is that we can quickly calculate the probable number of unique elements in a dataset with many duplicates,” said Patrick Ball, HRDAG’s director of research. “We can do a lot with this estimate.”


Reality and risk: A refutation of S. Rendón’s analysis of the Peruvian Truth and Reconciliation Commission’s conflict mortality study

Daniel Manrique-Vallier and Patrick Ball (2019). Reality and risk: A refutation of S. Rendón’s analysis of the Peruvian Truth and Reconciliation Commission’s conflict mortality study. Research & Politics, 22 March 2019. © Sage Journals. https://doi.org/10.1177/2053168019835628

Daniel Manrique-Vallier and Patrick Ball (2019). Reality and risk: A refutation of S. Rendón’s analysis of the Peruvian Truth and Reconciliation Commission’s conflict mortality study. Research & Politics, 22 March 2019. © Sage Journals. https://doi.org/10.1177/2053168019835628


Colombia (eng)

Text in English Assessing Claims of Declining Lethal Violence In March 2007, HRDAG published a study entitled "Assessing Claims of Declining Lethal Violence in Colombia." The authors of this report evaluated assertions that violence in Colombia declined after the demobilization of paramilitaries. They showed that these claims rest both on the overinterpretation of unadjusted data and on unsound causal inferences. The authors concluded that multiple data sources are needed to estimate the true rates of violence in Colombia after demobilization and they suggest avenues for further research. This research paper is also available in Spanish at ...

Judges in Habré Trial Cite HRDAG Analysis

Three months after the announcement of the momentous verdict finding former Chadian president Hissène Habré guilty of crimes against humanity, the presiding judges have released the full, written 681-page judgment of the court. Testimony given by HRDAG’s director of research, Patrick Ball, is mentioned at three points in the verdict. The judges included in their written judgment the HRDAG analysis that the mortality rate in Habré prisons was staggeringly high—much higher than the mortality rate among the population as a whole. Here’s an excerpt from the judgment, page 358 (translated by Google): The statistical expert, Patrick Ball, ...

Applications of Multiple Systems Estimation in Human Rights Research

Lum, Kristian, Megan Emily Price, and David Banks. 2013. The American Statistician 67, no. 4: 191-200. doi: 10.1080/00031305.2013.821093. © 2013 The American Statistician. All rights reserved. [free eprint may be available].


Press Release, Chad, January 2010

NEW STUDY DOCUMENTS HISSÈNE HABRÉ’S OVERSIGHT OF POLICE PRISONS WHERE THOUSANDS DIED 10th Anniversary of Indictment of Chad Ex-Dictator January 29, 2010, N’Djamena, Chad and Palo Alto, CA, U.S. - On the 10th anniversary of the first indictment of Hissène Habré in Senegal, the Benetech Human Rights Data Analysis Group (HRDAG) released a new study showing that the former Chadian dictator was well informed of the hundreds of deaths that occurred in prisons operated by his political police. This information could be critical in the long delayed prosecution of Habré who has been accused of killing and systematically torturing thousands of politi...

La importancia de la estadística

Patrick Ball (2018). La importancia de la estadística. Ibero. La revista de la universidad Iberoamericana. August-September 2018. © 2018 Universidad Iberoamericana Ciudad de México. Pp. 50-51.

Patrick Ball (2018). La importancia de la estadística. Ibero. La revista de la universidad Iberoamericana. August-September 2018. © 2018 Universidad Iberoamericana Ciudad de México. Pp. 50-51.


Using Cemetery Information in the Search for the Disappeared: Lessons from a Pilot Study in Rionegro, Antioquia

Tamy Guberek, Daniel Guzmán, and Beatriz Vejarano. “Using Cemetery Information in the Search for the Disappeared: Lessons from a Pilot Study in Rionegro, Antioquia.” In Methodological Proposals for Documenting and Searching for Missing Persons in Colombia. (Available in Spanish) © 2010 EQUITAS. All rights reserved.


Lies, Damned Lies and Official Statistics

This essay in the Health and Human Rights Journal addresses attempts to undermine Covid-19 data collection.

The Case Against a Golden Key

Patrick Ball (2016). The case against a golden key. Foreign Affairs. September 14, 2016.  ©2016 Council on Foreign Relations, Inc. All Rights Reserved.

Patrick Ball (2016). The case against a golden key. Foreign Affairs. September 14, 2016.  ©2016 Council on Foreign Relations, Inc. All Rights Reserved.


How many people have died in the Syrian civil war?


Justice Served in Guatemala: Testimonies from The National Security Archive & Benetech’s Human Rights Data Analysis Group


Unbiased algorithms can still be problematic

“Usually, the thing you’re trying to predict in a lot of these cases is something like rearrest,” Lum said. “So even if we are perfectly able to predict that, we’re still left with the problem that the human or systemic or institutional biases are generating biased arrests. And so, you still have to contextualize even your 100 percent accuracy with is the data really measuring what you think it’s measuring? Is the data itself generated by a fair process?”

HRDAG Director of Research Patrick Ball, in agreement with Lum, argued that it’s perhaps more practical to move it away from bias at the individual level and instead call it bias at the institutional or structural level. If a police department, for example, is convinced it needs to police one neighborhood more than another, it’s not as relevant if that officer is a racist individual, he said.


Guatemala: Access to Archives Sheds Light on Case of Forced Disappearance


Guilty Verdict and 40 year Maximum Sentence in Edgar Fernando Garcia Case


United Nations Issues Report on Deaths in Syria


Our work has been used by truth commissions, international criminal tribunals, and non-governmental human rights organizations. We have worked with partners on projects on five continents.

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