With regard to prison staff in the UK, I was in the prison service when the first cross sex postings were introduced. Selection of suitable staff was a careful and measured process - this would have been circa 1989, from memory.
Once it was established Prison Service policy, the gates (as it were) were open and any officer could apply. And did. Much of my time in the latter stages of my career was taken up with investigating allegations of staff misconduct - male prison officers engaging in inappropriate relationships with women prisoners. It was gross misconduct because of the clear power imbalance as well as the potential for corruption.
My investigations were the direct cause of seeing at least a dozen male prison officers given the boot but in any staff meeting, it was easy enough to pick out the male officers most likely to cross the line.
I doubt it's any better today. What l can't even begin to get my head around is a situation where women prisoners are forced to share communal areas with male bodied prisoners. These women are widely acknowledged to be a vulnerable and traumatised group who have poor coping strategies because of their histories of being abused.
Putting predatory males in women's prisons is an egregious policy and must be stopped. If the Daily Mail is starting to wake people up about the logical consequences, then I hope it continues by reporting on the reality in UK prisons today and why they are not safe for women who need women-only spaces.