In a society with near future levels of technology, the crime rate reached a high degree and the government decided to transform an island (which was a city) into a large prison, or an exile/banishment place.

This is the plan:

  • Building a wall around the island
  • Leaving only one bridge as a connection with the country
  • Sterilizing prisoners before banishing them
  • The prisoners can then live freely in the island


  1. How plausible is the idea of building the wall around the island?

  2. What kind of law enforcement units and technologies should be used to keep the situation inside the island under control?

  • 7
    $\begingroup$ You've basically written the background to John Carpenter's movie "Escape from New York" imdb.com/title/tt0082340 $\endgroup$
    – John Feltz
    Dec 15, 2016 at 18:19
  • 17
    $\begingroup$ Islands often come with seas around them, reducing the need for walls. $\endgroup$
    – Jon Hanna
    Dec 16, 2016 at 1:26
  • 1
    $\begingroup$ Just put "Snake" Pliskin on the case..... $\endgroup$
    – Thucydides
    Dec 16, 2016 at 3:41
  • 2
    $\begingroup$ an island as a prision? ... ah yes, just look to the australian government as inspiration $\endgroup$
    – John Hon
    Dec 16, 2016 at 8:10
  • 1
    $\begingroup$ Use two islands, one for each gender, solves all the problems with sterilization. $\endgroup$
    – John
    Dec 16, 2016 at 13:45

5 Answers 5


The Penal Colony has a long tradition of being a thing. From Alcatraz to parts of Australia, Tripoli to Isla Maria Madre, countries and empires have moved prisoners to hard-to-reach places, very often islands.

The great part of using an island is that the waters around the island become a wall for you. Alcatraz famously had treacherous waters surrounding it, which are cold and pulls things out to the to sea. This makes excessive walls unneeded. (Indeed, Alcatraz has walls, but this is very likely to separate prison populations and to protect the civilians on the island.)

So, if the island in question is small, a wall is easy to build. If it's large and the waters are particularly treacherous, then I wouldn't bother with a wall. A few speedboats is really all you need to patrol a small island. Add to this some normal prison offices on the colony, as well a substantial police force, and this penal colony is up and running!

As a bonus fact: Zxyrra noted that the sterilization of prisoners would be a human rights abuse. Since 1968, the ability to determine the number and spacing of children according to the "Proclamation of Tehran" and was reaffirmed as a human right by the UN General Assembly in 1969. Just thought you should know when you put that into your world!

  • $\begingroup$ Not to mention the (in)famous Devil's Island. $\endgroup$
    – jamesqf
    Dec 15, 2016 at 18:48
  • 1
    $\begingroup$ +1 Excellent answer, this summarizes what I was about to write. Consider also addressing the OP's suggestion of Sterilizing prisoners which may be considered quite the human rights abuse. $\endgroup$
    – Zxyrra
    Dec 16, 2016 at 3:59
  • $\begingroup$ Yes I think I will let down the idea of the wall, but for sterilization it's nearly impossible it will create social inequality in the futur. @Zxyrra what about a constant spray of colourless and odourless gas on the city that keep the prisoners sterilzed temporarily ? $\endgroup$ Dec 16, 2016 at 10:20
  • 1
    $\begingroup$ @AimanVargas You'd run in the same problems with birth control (pretty hard to sterilise a man without mechanical adjustments or permanent damage) and problems of running large-scale not-enclosed gas chamber on a hostile territory (ludicriously expensive). $\endgroup$ Dec 16, 2016 at 10:54
  • $\begingroup$ You could create a Prision in the middle of Antarctica. Without proper clothing and supplies, you wouldn't even need walls, because people would very likely freeze to death if they leave the prison building. The very idea of a prison colony is inacessibility especially without required equipment. It's also why the idea of a space prison is appealing in science fiction. $\endgroup$
    – Adwaenyth
    Dec 16, 2016 at 13:39

1: It depends on the island, but generally Yes.

If the geology of the island favours heavy construction around the coastline - that is, there's decent ground for foundations within a short distance of the shore - there should be no problem building a wall along it. Long walls have been built before, after all. As others have said, though, it's not really necessary - the water is your first line of defence, and all a wall is going to do is hide the prisoners from the view of the mainland.

2: This is the fun part.

This prison is going to be both completely unmanageable and political suicide for the leader who wants to build it.

You mentioned that prisoner's are being sterilised before being sent in there. Presumably, then, there's no intention of ever letting them out, and there's no gender segregation.

Can we say "holy crap"??

You said that

-The prisoners can then live freely in the island

Why do you want to provide law enforcement if they're supposed to be living freely on the island?

If you want to actually control the situation on the island, you're going to need soldiers - not cops, but soldiers, fully armed and ready to shoot at the slightest provocation.

After all, everyone on the island is a lifer - they have nothing to lose. There's no implicit or explicit threat of further punishment if commands are not obeyed. You don't have the normal structure of a prison, with its multiple independent security doors, remotely operated cells, regular access to shackles, etc.

This means that you can't use any of the normal procedures of a prison, or any normal police procedures. The only control you can exert over people in this situation is the threat and application of force, and that means soldiers. Heavily armed soldiers with enough ammo to mow down dozens of prisoners at a time.

You'll need enough of them to patrol the streets, conduct random searches of dwellings, and provide a mobile reserve to reinforce trouble spots. I don't have a calculation of how many that would be, I'm afraid.

Of course, this flies in the face of the idea of the prisoners living freely on the island.

If the prisoners are living freely on the island, mob rule is going to be quickly enforced. Tribalism is the most basic form of human society, and it's one we're still hard-wired to follow; it will almost certainly emerge in this prison, fast and hard. After all, this is a prison - you're not putting in a bunch of easygoing folks, you're going to be putting in a high proportion of violent individuals, many of whom probably come from a background in gangs.

So, the gangs are going to re-form on the inside, and start claiming territory and resources. Resources will include slaves. The majority of women in there will likely be enslaved in short order.

You've set up a scenario in which there are no moderate outcomes - you can either police with extreme force, or you can give up and allow mob rule. Neither of these options is going to make whichever politicians or legislature comes up with the idea very popular.

  • $\begingroup$ Yes yes "holy crap" that's the right word. So the idea is a mob rule inside the island with high technology of surveillance, and a police with extreme force outside $\endgroup$ Dec 16, 2016 at 10:45
  • $\begingroup$ @AimanVargas I believe that was two words. $\endgroup$ Dec 21, 2016 at 23:52
  • $\begingroup$ This didn't happen to Australia, even though it started as a penal colony. $\endgroup$
    – vsz
    Dec 22, 2016 at 7:22

TL,DR: You'll get a mass escape leading to a civil war that will result in the downfall of the government which set this up, and the rise of a 'rogue state'.

You're headed for trouble. You've filled a modern island city with the worst criminals you can find, have set them loose, and have given them a reason (forced sterilisation and incarceration in an unregulated environment) to be very angry with you.

The resources available in a city are substantial, and in the likely event that the prisoners organise themselves to escape, you could find yourself facing an army armed with whatever they can make in their city. Given near-future tech, which may include 3D printers, machine shops and whole factories, these probably won't be "improvised" weapons either.

I'll be the first to admit that there will probably be a large number of rapes and murders when the prison is first established, but these won't last. Humans instinctively organise themselves, and it is in the interests of the prisoners to exercise self-control. Those who can't will most likely be "selected against" sooner or later, leaving the more rational, organised criminals.

In order to prevent this, it will be necessary to have an extreme level of surveillance, and to be prepared to kill any prisoner who appears to be organising an escape, no matter how far in the future the preparations seem to suggest that the escape will take place. Even if you implant explosives in each prisoner while sterilising them, if you miss even a few prisoners neutralising their implanted bombs or tampering with surveillance devices, they'll eventually cripple your whole surveillance network and prepare their breakout unobserved. The level of surveillance required would be such that it would be cheaper to have a regular prison with guards on-site. Implanted bombs would also have their own political cost, and I doubt that a government sufficiently lax or deluded to think that this sort of prison is a good idea would go that far.

Additionally, in an area the size of a city, there will be ample opportunity for the prisoners to establish farms, thus securing their own supply of food. It is always possible for the authorities to simply destroy any farms they spot, but doing so would likely have consequences that the authorities were trying to avoid when they created this prison: the problems associated with expanding the range of crimes attracting the death penalty, and the monetary cost of supplying the prisoners with outside food as opposed to the political cost of allowing - or forcing - the prisoners to starve.

In such a situation, without adequate control of the prison environment, regardless of surveillance and remote prisoner termination capabilities, I believe that a successful mass escape is inevitable. The escapees won't necessarily include the insane or disorganised prisoners who cannot control their impulses, since these will most likely have been "selected against", so the escapees will most likely resemble something that you might call a "mafia army"; organised, disciplined and ruthless in a way that regular army recruits or volunteers are seldom capable of.

It is a fact that many normal soldiers, particularly conscripts, have difficulty killing another human. Normal humans are societally and genetically programmed against killing, and in combat, it is not unknown for a soldier to fail to fire or to deliberately miss. It takes quite a bit of combat experience (not just training) for a soldier to overcome this and to be fully effective.

However, this "mafia army" would already have been selected to include people who were either murderers before their incarceration, or who - due to the initially unregulated environment - have already been exposed to combat conditions. With even a few real soldiers included in the prison population, it can be almost guaranteed that the "Mafia Army" will be more effective than any unit of free soldiers unless those free soldiers also have actual combat experience.

The difference between this situation and other real prisons is that real prisons are either regulated internally by the authorities (e.g. Alcatraz), or if internally unregulated, the authorities can be confident that they have excluded any significant manufacturing capability and have control over supply.

Once an escape has been achieved, the escapees will likely be loose in sufficient numbers that recapturing them all - if they split up - would be a massive undertaking, and by retaining a degree of organisation, the escapees could act to secure their long-term freedom - by eliminating the government that imprisoned them in the first place.

Given that an escape may take years to organise, it is likely that the escapees wouldn't all simply go their own way once they were free - the prisoners who are likely to do that are also more likely to have transgressed against the prison's evolved set of laws and to have been disciplined or eliminated. This would leave the escapees loose in their parent society effectively as a guerilla army. With sufficient numbers, they could conceivably replace the government of their parent society with their own, or at the least cause internal strife for years to come.

Finally, don't think that because you've sterilised these criminals that they won't find a way to reproduce. Unless you castrate or spay them (physically or radiologically), effectively removing the testes or ovaries and potentially the penis or uterus too - with the attendant political fallout that will accompany the procedure - it is possible to reverse most methods of sterilisation, and you've probably included prisoners with sufficient education to perform such reversals, whether actually qualified or not.

Even if you really sterilise these criminals, and perform radical castrations with penectomies or hysterectomies with removal of the ovaries, it is not beyond the bounds of possibility (in a place as large as a city) that a few prisoners might not be able to perform stem-cell research that could result in restoration of these organs. Even if this doesn't happen, criminality is more than just genetics, it is also a mindset that can be instilled during childhood. If irreversibly sterilized prisoners escape, they could conceivably adopt children young enough to be sufficiently mentally malleable to be shaped into the next generation of criminals. Hence, while not genetically related to their adoptive parents, these children would still be the ideological offspring of their adoptive parents.

In the not unlikely event that criminals escaped from this prison take over the government of their parent nation, this nation would most likely come to be viewed as a rogue nation, on the order of Iraq (under the Hussein regime) or present North Korea. If this happened in a nation like the USA, it could end up as a global catastrophe...

  • 1
    $\begingroup$ If you have machine shop you don't need 3D printers to make guns (unless you think of metal-printing ones but good CNC mill would cover most of uses for less price). Also, after hierarchy is established, government can strike deals with prison leaders. While having a new country full of people who have good reasons to be angry with you right at your borders is not good, islanders don't have enough high tech to engage in modern warfare, so attempts at expansion would end up droned down or something like that. $\endgroup$ Dec 16, 2016 at 11:06
  • $\begingroup$ Your answer gave me a lot of ideas for the plot hahah ! I admit that mass escape is inevitable, but like you said it will take years to organise, and with a good surveillance technologies (a stunning Matt's bracelets that can blow up) it will give me more "peace time" to write my story before things goes bad. $\endgroup$ Dec 16, 2016 at 11:10
  • $\begingroup$ @Daerdemandt, I was thinking that "machine shop" would also cover gun production, but metal-capable additive devices would also be feasible in a near future setting. The mafia army doesn't need to be able to win in a stand-up fight, its best option is asymmetric warfare after the escape. These criminals have the advantage of ruthlessness uncompromised by political necessity - they're already the "bad guys", so the public will expect them to be bad. I might expect a deal with the emergent leaders of the prisoners, but no sensible politician ought to trust these people in the slightest. $\endgroup$
    – Monty Wild
    Dec 18, 2016 at 22:18
  • $\begingroup$ @MontyWild Metal 3D printers are fun and high-tech, but using them to make guns when you have machine shop is like hammering nails with a microscope. Stationary one. For the same price, regular machining method would give you more throughput and better surfaces. You won't be able to make some exquisite pieces - but guns are designed to be machined, not printed, so you're fine there. $\endgroup$ Dec 18, 2016 at 23:03

Why build a wall? Water is pretty easy to patrol, and a freely-living population with a whole city to play with wouldn't have much difficulty overcoming any wall you might build.

As for question 2, it really depends on what you mean by 'under control'. If you want proper, Western-style prison control then you'll want some guards and use the same technology and procedures as prisons do now. You could throw in a few extras - perhaps a stunning ankle bracelet* or similar.

If you just want to stop the situation inside the prison affecting the situation outside, then just shoot anyone who tries to leave and let them get on with it, with a regular food drop.

*Stunning as in 'like a tazer', not stunning as in 'oh wow, your bracelet is sooooo beautiful!'

  • 3
    $\begingroup$ @PipperChip Its shocking how nice that ankle bracelet looks. $\endgroup$
    – kingledion
    Dec 15, 2016 at 18:12
  • $\begingroup$ @PipperChip It's positively electrifying. $\endgroup$ Dec 21, 2016 at 23:53

Don't think of it as a prison, think of it as exile. The difference between that and a prison colony (as mentioned by PipperChip) is that there is not even a pretense of responsibility for those inside. They can farm and fish for food, or not, as they please. They can elect a government, or not, as they please.

Completely insane in real life, but possibly a good setting for a story.

  • A "failed state" like this on the border will be a constant source of instability. If it is large enough for the inmates to feed themselves with primitive agricultural techniques, the border to too long to control properly. So how do you stop the inmates from growing weed instead of potatoes and bribing guards to smuggle it out?
  • If the exile society comes apart, any prison sentence may be seen as something close to a death sentence. You wrote that crime rates are soaring -- what happens if respectable citizens find out that their nephew is going to be exiled for a "youthful indiscretion"?
  • 1
    $\begingroup$ I think this answer would be better if it outlined at least some of the reasons why it would be insane in real life. Doing so could add elements of realism to a story set with such a setting. $\endgroup$
    – user
    Dec 15, 2016 at 21:02
  • 1
    $\begingroup$ > what happens if respectable citizens find out that their nephew is going to be exiled for a "youthful indiscretion"? They will not vote for "tough on crime" judge on the next election. $\endgroup$ Dec 16, 2016 at 11:08

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .