The director of the office of the judicial inspectorate of prisons, Gideon Morris, said gang tribunals sentenced errant gang members, or prisoners who refused to join them, to be raped by HIV-positive inmates.
Sometimes, the rape would be carried out by one person, sometimes by several.
"They give him a "slow puncture", meaning he will die over a peiod of time," Morris told the commission.
He had first heard of
the punishment about six months ago, in the
"It's a new phenomenon," he said.
If that inmate died in prison of Aids-related conditions, it would be recorded as a natural death.
He also said the number of prisoners who died of natural causes rose 528%, from 186 in 1995 to 1 169 last year, an increase considerably higher than the 38% increase in prison population.
High demands on immune systems
Morris said: "The poor hygienic conditions caused by overcrowding are placing high demands on the immune systems of prisoners, and this seems to contribute to this escalation in the number of natural deaths.
"Even the most-healthy person would find it difficult to remain healthy if he or she was locked up in some of these prisons."
Added to this was the increased number of HIV/Aids prisoners admitted from outside prison, he said.
Replying to a question
from the commission's leader of evidence, Vas Soni, he said it was difficult to
say whether Aids was the largest cause of death.