I shadowed a colleague today. She is a drugs worker who works with drug users who have entered the criminal justice system (I work with drinkers who end up in hospital).
My colleague took me on her round at Stevenage police station's cells. Here in Britain we euphemistically call our holding tanks custody suites.
At Stevenage custody suite, all prisoners have their shoes confiscated, including those without laces. They are given rubber beach sandals to wear. A very sensible policy in my opinion.
Shoes off in the house; shoes off in the cells.