I'm still exploring other possibilities, but the strongest theory right now is that we're dealing with an actual physical case of the many worlds theory, or multiple dimensions. You might've noticed in the welcome message that your imprisonment is for "the good of your individual timeline", which leads to the natural conclusion that there are multiple versions of each inmate that's been brought here - or rather, that the timeline our Warden has deemed as criminal, has been redirected into Marina. There's still a version of us back home that allegedly follows a different timeline and won't be committing the crimes we're accused of committing. In fact, it's been claimed that the people back home won't even notice that we're missing.
There's been several reported cases of multiple versions of the same individual residing simultaneously in the dome, simply because they originated from separate timelines or dimensions. Others have been here and then disappeared, only to return later on with or without the memories of their previous stay.