Poor technology (most government technology is poor) and poor communications between prisons, the courts and the Ministry of Justice is one factor. Much of the processing still uses pen and paper, with old fax machines used for communications.
There are also clerical errors such as the one we saw with one of the releases this week, where a prisoner received an immediate custodial sentence but it was entered on the system as a suspended sentence.
Prison staff are having to work out release dates by hand due to the failure of a computer system that was supposed to do the job. And calculating release dates has become more complicated. Until 2020, almost all offenders with fixed length sentences were released after serving half their sentence, serving the rest under probation. Now, some are released after 40% of their sentence, some after 50% and some after 66%.
Inexperienced staff are having to process large numbers of prisoners. More than half of prison officers have been in the job less than 5 years, with one quarter having less than 2 years experience. Go back to March 2010 and more than 75% had been in the job for 5 years or more.
Perhaps the biggest problem is that, for the last 25 years, successive governments of all colours have failed to build enough prison places to cope with demand. Our prisons are overcrowded. Wandsworth, which was the prison involved in the two most recently reported errors, has almost twice as many prisoners as it was designed to hold. One quarter of prisoners are in cells that don't meet fire safety standards (that's everywhere, not just Wandsworth). Violence in prisons has rocketed. Two thirds of prisoners spend 18 hours or more per day locked in their cells. Prisoners struggle to get toilet paper for their cells and may have to choose between a shower and a hot meal. And prisons are understaffed. All this puts pressure on staff and leads to an environment where mistakes become more likely.