From speeding fines to determining how long police can track a suspect, algorithms seem good at doling out justice – but their objectivity maybe an illusion

Tracked, but for how long? (Image: Tomasz Zajda/Alamy)

NINE years ago, federal agents stuck a location tracker on a nightclub owner’s car without a warrant. The agents thought their suspect might be dealing drugs, and four weeks of GPS data ultimately proved them right. He countered that the prolonged tracking had violated his privacy, and therefore his constitutional rights. The case fell apart in the Supreme Court, where justices debated the length of time that police could tail citizens before routine investigation became all-out invasion. Was four weeks too long? What about three days, or four hours?

Last week, a high-tech solution was proposed: let algorithms set the guidelines for us. Since computers are able to unearth subtle patterns in data, the thinking goes, they could help lawmakers quantify how much or how little surveillance is fair.

“Some justices think four weeks is too much and they’ve never been able to explain why,” says Steven Bellovin at Columbia University in New York City. “I saw there was a natural way to answer some of the questions by using these techniques.”


Bellovin, along with specialists in computer science and law, analysed previous research on tracking to learn what such data could uncover about an individual’s characteristics and daily habits. They concluded that one week of data would reveal enough information to constitute a threat to privacy, and so would be a reasonable place for the law to draw the line (NYU Journal of Law & Liberty, doi.org/s5d).

They also suggested taking the process a step further, using algorithms to set different limits for different enquiries into a suspect’s personal life, such as their drug habits.

Other legal questions could be solved in a similar manner. Take gerrymandering, when politicians try to draw new boundaries around electoral districts to better suit their party’s goals. A trained computer program – like the one developed by software engineer Brian Olson earlier this year – could impartially divide up the population, leaving individual human interests out of the equation.

Since computers are so sensitive to patterns in data, they can help us create more nuanced rules, says Nick Wagoner, a lawyer in Houston, Texas.

Some have even proposed making an algorithm the law itself, with tools that could automatically sniff out contract violations, problematic patents or election fraud. Lisa Shay at West Point in New York and colleagues have suggested rewriting “amenable laws” – those that deal with clear-cut cases of right and wrong – so that algorithmic law enforcement could understand them. They have already attempted to build computer systems that can issue speeding tickets.

We shouldn’t expect to see computers sitting in the judge’s chair any time soon, says Harry Surden at the University of Colorado. He warns that bringing machines into the law could imbue us with a false sense of accuracy. Two algorithms could take the same data and come up with different analyses, he says. He can even imagine a time when the prosecution and the defence pit their “expert” machines against each other.

“We have to be very cautious to not overly endow things that look technological and mathematical as objective,” Surden says.

We have to be careful not to see things that look technological and mathematical as objective

This article appeared in print under the headline “The judge is a robot”