A stuffy, overcrowded cell. At times, two or three men to a single bunk. Lockdown for 23 out of 24 hours.

Is this what awaits South Africa's Oscar Pistorius if he is not released on bail while he awaits trial for the murder of his girlfriend?

Some of South Africa's prisons are better than others.

But whichever one might house Pistorius, there's no question that conditions would be a far cry from those in his $560,000 home in the luxury Silverwoods Estate, on the outskirts of Pretoria.

South African prisons are frequently overcrowded, putting a strain on sanitation, ventilation and medical care, according to Nooshin Erfani-Ghadimi, project coordinator for the Johannesburg-based Wits Justice Project , a civil society group.

The overcrowding means three men may share a single cell, or communal cells for 40 people are jammed with double the number they were intended to hold, with men sleeping in double or triple bunks, she said.

"We heard of one person who for the first year in remand detention slept on the floor and then 'graduated' to a bunk," she said. Remand is the term used for pretrial custody.

Many inmates are kept locked up for 23 hours a day, with only an hour outside their cell. Some prisons go into lockdown as early as 3 or 4 p.m., leaving prisoners cooped up for 12 hours or more at a stretch.

"It's not a pretty picture," Erfani-Ghadimi said.

Overcrowding is a particular problem in remand prisons, where it runs at just over 200%, she said, citing figures from the Department of Correctional Services. Overall, overcrowding in prisons stands at about 133%.