Could a self-monitoring system for criminals replace prisons one day?

In the 2020s, the US was spending an eye-watering $182 billion a year on locking up its citizens. No other country imprisoned as many people or spent as much in doing so. And the US wasn’t alone: prisons in many countries around the world were overcrowded, inhumane and expensive. So why not just get rid of them? This became possible when technology was developed so that people could be monitored and detained at home – and when society caught up to the benefits.

The HomeGuard scheme, which replaced traditional prisons, comprised three elements. The first was an ankle bracelet that monitored the prisoner’s precise location. The second was a harness containing sensors that recorded what the person was doing and saying. If the terms of the sentence were broken – for example, by the prisoner departing from the agreed area of confinement or engaging in illegal behaviour – the third element kicked in: the person was temporarily incapacitated by an energy device similar to a stun gun. Prisoners soon learned the rules.

It’s no surprise that the first countries to abolish prisons were Scandinavian, where incarceration was viewed as a way to safeguard the rest of the community, rather than a means of enforcing punishment. (“HomeGuard” is a translation of the Norwegian word hjemmevernet.)

Halden Prison, a maximum-security facility in Norway, opened in 2010 with unbarred windows, ensuite bathrooms in cells, TVs and high-quality furniture. Inmates ate food and played games with unarmed prison officers, not guards, and were encouraged to work for money. Baffled outsiders compared the prison to a comfortable hotel. By contrast, in US facilities in the first quarter of the 21st century, prisoner abuse was widespread. Recidivism in Norway was around 20 per cent after two years, compared with 50 per cent in the UK and 60 to 70 per cent in the US. Halden was expensive, but prisoners were rehabilitated into society more effectively, which saved money in the long term.

Even in progressive Scandinavia, some members of the public felt that wrongdoers should be punished. However, sociologists found that if the public are shown that excessive, brutal and gratuitous punishment is bad for society and doesn’t protect the community, they can be convinced that another method is better. This is what HomeGuard set out to do.

The first selvfengsel (“self-prison”) trial was launched in 2030 in Norway. Prisoners were fitted with secure ankle bracelets transmitting a GPS location signal, and a harness was worn that constantly filmed the face of the prisoner and ran it through face-recognition software. This prevented individuals from passing the sensor harness to another person. Artificial intelligence monitored the actions of the prisoner – for example, keeping check of what websites they visited and the messages and calls they made.

Action was taken if the terms of their sentence were violated. A conducted energy device is the hardware typically used in a stun gun. Integrated into a prisoner’s ankle bracelet, it delivered an electric shock if the AI monitoring system determined a breach of sentencing rules had occurred. Law enforcement officers were then alerted.

The HomeGuard scheme was designed following a proposal in 2018 by Dan Hunter at King’s College London and his colleagues. They calculated that even if prisoners were refitted with new tech each year, self-prison cost tens of thousands of dollars less than traditional prison over the course of a person’s sentence. And the price came down further as the technology got cheaper.

Initially, selvfengsel was trialled in Bergen. All prisoners not convicted of capital offenses (or crimes of equivalent severity) were fitted with self-prison tech and sent home. The scheme was a huge success financially, which helped with the social message: brick-and-mortar prisons were expensive, inhumane, ineffective and archaic. For the rest of the world watching the trial, it became obvious that conventional prisons didn’t adequately protect society because of high recidivism rates.

Technological incarceration was better all round, and selvfengsel soon spread across the rest of Scandinavia. Trials then took place across Europe and also in India, Mexico, Brazil, Australia and even the US. By 2050, 95 per cent of prisons in those countries had closed. The savings were invested in education and healthcare. Crime rates fell both because of the societal improvements and because the stigma of being constantly monitored was a powerful incentive to stay on the straight and narrow. Parents said to their children, “don’t break the law or you’ll go to self-prison,” and the threat was sufficient.

Rowan Hooper is New Scientist‘s podcast editor and the author of How to Spend a Trillion Dollars: The 10 global problems we can actually fix. Follow him on Bluesky @rowhoop.bsky.social. In Future Chronicles, he explores an imagined history of inventions and developments yet to come.