To this it might be sufficient to reply that this is already done; twenty years' immurement is a very common sentence passed upon wrong-doers, and in some cases the law goes as far as to inflict penal servitude for life.
"In-Darkest-England-and-the-Way-Out"
Booth, William
There are three periods of immurement.
"Castles and Cave Dwellings of Europe"
Sabine Baring-Gould
There have been horrible instances of voluntary immurement in Christian Europe, and above all in the Christian East; but not quite-though very nearly-as bad as this.
"Castles and Cave Dwellings of Europe"
Sabine Baring-Gould