Exact logistics will vary from facility to facility, from state to state, and from one level of offender to another (and jails are different from prisons). My experience is based on Kansas, state-level, at several different facilities. This is the “family and friends” experience; professionals such as lawyers and doctors go through a similar but not identical version.
First, visitors must be on the approved list. You submit an application for who you want to see, with your name, address, ID, and relationship. They’ll weed out, or at least give extra scrutiny to, those whose purposes may be improper–people with criminal records, co-defendants, the offender’s victims, and so forth.
The prison will have regularly scheduled visiting hours, usually on the weekends. Visitors have to present acceptable ID, be checked off on the approved list, and go through security–metal detector, turn your pockets inside out, maybe take off your shoes. What you can take inside is extremely limited: your essential medications, money for snacks, photos to share, sometimes legal papers or a bible. Usually, you go through some version of sally port: one door closes behind you before the next one opens.
At “supermax” type facilities or if the inmate is in segregation, visits will be through glass or even over video link. At ordinary facilities, even maximum-security, typically the inmates and visitors will be in one or several large rooms, with long rows of tables/chairs and officers walking around patrolling. You’ll be surprised at the number of kids, even little kids, and a children’s play area is pretty common. Husbands and wives get a quick kiss at the beginning and end of visits (and a quick grope when the guard isn’t looking). Visits are usually several hours if not all day, so food is available (maybe vending machines, maybe a full snack bar operated by inmates, with hamburgers, pizza, and ice cream). The facility will usually have games (cards, dominoes, scrabble, etc.) and religious texts to help pass the time.
If one of the prison’s regularly-scheduled counts occurs during the visit, everything is locked down–visitors can’t arrive or leave until all inmates are accounted for. At one Kansas facility, the visitor restrooms are outside the sally port, so the officers will announce, “Count will be in 15 minutes; if you need to use the restroom, now’s the time.” Once the count starts, you’d better not need to go for the 30-60 minutes it takes to clear. At other prisons, there’s a visitor restroom in the visiting room; the guard will unlock it upon request. Inmates have their own restroom, and have to be patted down or searched before they can use it.
When the visit is over, the inmate will be strip-searched, and the visitor(s) can’t leave until the inmate is cleared.
Professional visits are similar, but typically have to be scheduled in advance. I attended a deposition of an inmate once; the general procedure was the same, although obviously more materials could be taken inside (the court reporter had her recording equipment, e.g., and everybody involved had binders and notepads and pens). We were placed in a small conference room somewhere in the administration building; the inmate was brought in by a guard, but the guard left after delivering him, and was summoned back to pick him up after it was over. Again, the inmate had to clear a search before we were allowed to leave.
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