Archive for crime prediction

El asiedo [book review]

Posted in Books, pictures, Travel, Wines with tags , , , , , , , , , on January 13, 2018 by xi'an

Just finished this long book by Arturo Pérez-Reverte that I bought [in its French translation] after reading the fascinating Dos de Mayo about the rebellion of the people of Madrid against the Napoleonian occupants. This book, The Siege, is just fantastic, more literary than Dos de Mayo and a mix of different genres, from the military to the historical, to the criminal, to the chess, to the speculative, to the romantic novel..! There are a few major characters, a police investigator, a trading company head, a corsair, a French canon engineer, a guerilla, with a well-defined unique location, the city of Cádiz under [land] siege by the French troops, but with access to the sea thanks to the British Navy. The serial killer part is certainly not the best item in the plot [as often with serial killer stories!], as it slowly drifts to the supernatural, borrowing from Laplace and Condorcet to lead to perfect predictions of where and when French bombs will fall. The historical part also appears to be rather biased against the British forces, if this opinion page is to be believed, towards a nationalist narrative making the Spanish guerilla resistance bigger and stronger than it actually was. But I still read the story with fascination and it kept me awake past my usual bedtime for several nights as I could not let the story go!

To predict and serve?

Posted in Books, pictures, Statistics with tags , , , , , , , , , , , on October 25, 2016 by xi'an

Kristian Lum and William Isaac published a paper in Significance last week [with the above title] about predictive policing systems used in the USA and presumably in other countries to predict future crimes [and therefore prevent them]. This sounds like a good idea for a science fiction plot, à la Philip K Dick [in his short story, The Minority Report], but that it is used in real life definitely sounds frightening, especially when the civil rights of the targeted individuals are impacted. (Although some politicians in different democratic countries increasingly show increasing contempt for keeping everyone’ rights equal…) I also feel terrified by the social determinism behind the very concept of predicting crime from socio-economic data (and possibly genetic characteristics in a near future, bringing us back to the dark days of physiognomy!)

“…crimes that occur in locations frequented by police are more likely to appear in the database simply because that is where the police are patrolling.”

Kristian and William examine in this paper one statistical aspect of the police forces relying on crime prediction software, namely the bias in the data exploited by the software and in the resulting policing. (While the accountability of the police actions when induced by such software is not explored, this is obviously related to the Nature editorial of last week, “Algorithm and blues“, which [in short] calls for watchdogs on AIs and decision algorithms.) When the data is gathered from police and justice records, any bias in checks, arrests, and condemnations will be reproduced in the data and hence will repeat the bias in targeting potential criminals. As aptly put by the authors, the resulting machine learning algorithm will be “predicting future policing, not future crime.” Worse, by having no reservation about over-fitting [the more predicted crimes the better], it will increase the bias in the same direction. In the Oakland drug-user example analysed in the article, the police concentrates almost uniquely on a few grid squares of the city, resulting into the above self-predicting fallacy. However, I do not see much hope in using other surveys and datasets towards eliminating this bias, as they also carry their own shortcomings. Even without biases, predicting crimes at the individual level just seems a bad idea, for statistical and ethical reasons.