Cortical Stacks serve as a receptacle for the human consciousness or Digital Human Freight (D.H.F.). All citizens within the Protectorate have a cortical stack implanted when they are one year old. Cortical Stacks are composed of a non-terrestrial metal left by an Alien civilization, along with astrogation charts mapping several habitable planets within the galaxy. Cortical Stacks were originally developed as a means of interstellar travel to reach these planets. By downloading the human consciousness, they were able to transmit it to a waiting body or "Sleeve" on a distant planet. This method of transmitting consciousness off-world, called Needlecasting, allowed instant travel to anywhere in the Settled Worlds that otherwise would take centuries to reach by traditional means. Over time, this technology would become a method of immortality for those who could afford it. Placing the dead in new bodies, called "Re-sleeving", can be accomplished by simply downloading consciousness in a new Sleeve after death as long as the Cortical Stack is intact after sleeve-death. Citizens who cannot afford re-sleeving or do not want to be re-sleeved, have their Cortical Stacks placed in a storage facility after sleeve-death, where they can remain indefinitely. Because of the nominal ability to revive anyone who dies, sleeve-death, so long as the cortical stack remained intact, was reduced to a lower level of legal concern, akin to property damage. Only if the stack was destroyed was such considered death or, if the result of violence, murder. It became common practice for the state to guarantee re-sleeving for victims of accidents or crimes, should they not specify their objection to being re-sleeved, although this re-sleeving was often done using whatever sleeves were available, regardless of quality or appropriateness, unless the individual had made other, usually extremely expensive, prior arrangements. Care must be taken to avoid real death, as anything from blunt trauma to energy weapons fired at the stack (known as slagging) can destroy the stack.