I no longer bother to link to bent cops - there are so many cases these days that it simply isn't worth mentioning and anyway many are victims of the "unvanishingly common" False Allegations Industry.
But it's worth showing this - in my experience 90% of prison officers are decent people trying hard to do a very difficult job (ditto police).

The few Rotten Coppers poison the rest but the REAL problem is the bosses - who ascend the slippery pole by allowing, encouraging and protecting the Wayne Cousins types.
And the training (or lack of it) which allows those in power to feel they can get away with it.

www.bbc.co.uk/news/uk-england-merseyside-63558747

There's an article about a killer police officer attached to the one you posted about prison conditions.

We can stop the police brutality that killed Dalian Atkinson, but let’s first admit there is a problem - Leroy Logan

... Many people say it’s the “a few bad apples” scenario. However, I have always asked myself, “What are the good apples doing about it to challenge the excessively violent officers?” ...