Computers are getting pretty good at predicting the future. In many cases they do it better than people. That's why Amazon uses them to figure out what you're likely to buy, how Netflix knows what you might want to watch, the way meteorologists come up with accurate 10-day forecasts.

Now a team of scientists has demonstrated that a computer can outperform human judges in predicting who will commit a violent crime. In a paper published last month, they described how they built a system that started with people already arrested for domestic violence, then figured out which of them would be most likely to commit the same crime again.

The technology could potentially spare victims from being injured, or even killed. It could also keep the least dangerous offenders from going to jail unnecessarily. And yet, there's something unnerving about using machines to decide what should happen to people. If targeted advertising misfires, nobody's liberty is at stake.