It's very difficult to see who is responsible for this, if they were tried before a jury with each case on its merits. What is important is they are all properly compensated and anyone trying to cover anything up also prosecuted. You can't really blame a prosecutor for dropping an unreliable expert witness. Fujitsu in the UK was mainly made up of ex-ICL employees, I suspect you'd find it very difficult to find an IT expert in the whole company.
you can if they had full knowledge that said witnesse was unreliable
and by all accounts lied under oath in a court
fugitsu have repeatedly declined to comment
at least one of the sub post masters committed suicide ?
a 19 year old spent 3 months in Holloway prison
criminal record which hampered her job / life prospects for 20 odd years
sub post masters who paid money back to the post office out of there own savings so they did not end up in jail
sort of settled out of court which has relevance to another thread in here
Sub post masters interviewed under caution and lied to by post office investigators
told they were the only one that claim it was the fault of horizon