Post Office Horizon IT scandal
Notes by Stephen Mason, April 2025
The
Post Office Horizon IT scandal is the worst in British history, although
England & Wales is the most shameless.
It
is caused by a number of factors, including the presumption that computers are
reliable (whatever reliable means, for which see the articles below).
If
this presumption did not exist, the Post Office and other prosecutors might not
have succeeded in the nefarious way they did.
I am the only lawyer that has considered this in detail and have done so
since the second edition of Electronic Evidence in 2010.
The fact is, the main legal problem that the subpostmasters and
subpostmistresses faced is the failure of lawyers (both solicitors and
barristers) to understand electronic evidence and the failure of judges to
order disclosure of relevant evidence (the case of Seema Misra illustrates
this, for which see the transcript of her trial below and the practitioner
textbook for judges and lawyers, also below).
Precis of the issues
These two short articles set out the issues
concisely:
Stephen Mason, ‘The presumption that
computers are reliable’, Counsel, July 2024, 34-6, https://www.counselmagazine.co.uk/articles/the-presumption-that-computers-are-reliable
(in this article I explain the 2 ways of approaching the presumption that
computers are reliable)
Stephen
Mason, ‘The cause of the Post Office Horizon scandal? The Law
Commission? Judges? Lawyers?’ Computer Weekly, 1 November 2023, online
The
Briefing Note below was written for Members of Parliament:
Nicholas Bohm, James Christie,
Peter Bernard Ladkin, Bev Littlewood, Paul Marshall, Stephen Mason, Martin
Newby, Steven J. Murdoch, Harold Thimbleby and Martyn Thomas CBE, ‘Briefing Note: The legal rule that
computers are presumed to be operating correctly – unforeseen and unjust
consequences’, 19 Digital
Evidence and Electronic Signature Law Review (2022) 123 – 127
https://journals.sas.ac.uk/deeslr/article/view/5476
Stephen Mason, ‘The UK Post Office Horizon IT scandal: Part 1: an
outline of the chronology’, (2024) 30 Computer and Telecommunications Law
Review, Issue 3, 59-63
Stephen Mason, ‘The UK Post Office Horizon IT scandal, Part 2: the legal
issues’, (2024) 30 Computer and Telecommunications Law Review, Issue 4, 96-101
The presumption that computers are reliable
For a full treatment of this presumption, demonstrating the fact
that software is not reliable, see chapter 5 of the open-source
practitioner text for judges, lawyers and legal academics: Stephen Mason and
Daniel Seng, editors, Electronic Evidence and Electronic Signatures (5th
edition, Institute of Advanced Legal
Studies for the SAS Humanities Digital Library, School of Advanced Study,
University of London, 2021)
https://uolpress.co.uk/book/electronic-evidence-and-electronic-signatures/
For a devastating and
damming review of the Law Commission’s arguments leading to the recommendation
that computers should be presumed to be reliable, see:
James Christie, The Law Commission and section 69 of the Police and
Criminal Evidence Act 1984, 20 Digital Evidence
and Electronic Signature Law Review (2023)
62 – 95
https://journals.sas.ac.uk/deeslr/article/view/5642
The
Post Office (31 July 1995), Inland Revenue (16 October 1995), BT (27 October
1995), CPS (1 November 1995) and DTI (9 November 1995) wrote to the Law Commission supporting the
presumption that computers are reliable. I published each of their responses in
2023:
https://journals.sas.ac.uk/deeslr/article/view/5649
2010 Seema Misra
When I became aware of Seema Misra’s case, I contacted her lawyer (Issy
Hogg) to offer help and point out our book. I was not asked to help (although I
offered my help for free). I obtained the permission of the judge to buy and publish
the transcript of her trial in the journal I founded (Seema Misra also agreed
to publication), which indirectly helped the scandal increase pace against the
Post Office
https://journals.sas.ac.uk/deeslr/issue/view/328
Tim McCormack, ‘The Post Office Horizon system and
Seema Misra’ 13 Digital
Evidence and Electronic Signature Law Review (2016) 133-138
https://journals.sas.ac.uk/deeslr/article/view/2303
Court of Appeal misunderstanding of software
Peter Bernard Ladkin, Stephen Mason and Harold Thimbleby ‘Misunderstanding
Digital-Computer Technology in Court: A Commentary’, 21 Digital Evidence and
Electronic Signature Law Review (2024), 1-13
https://journals.sas.ac.uk/deeslr/article/view/5776/5406
Articles dealing with how a legal system can approach evidence in
electronic form – the articles below refer to all legal proceedings in any
jurisdiction – they are not limited to England & Wales
Michael Jackson, ‘An approach to the judicial evaluation of evidence
from computers and computer systems’ 18 Digital Evidence and Electronic
Signature Law Review (2021) 50-55
https://journals.sas.ac.uk/deeslr/article/view/5289
The
article below is a slightly revised version of a report submitted to the
Ministry of Justice in response to the invitation by Mr Alex Chalk MP, then
Parliamentary Under-Secretary of State (now Solicitor General), to Paul
Marshall, Barrister, in August 2020 to prepare a paper on proposed
recommendations for improving the existing approach under rules of court for
the disclosure in court proceedings of computer-derived evidence. The paper was
submitted to the Ministry of Justice in November 2020. The paper is understood
to have been referred by the Under-Secretary of State to the Attorney General
and the Chair of the Criminal Procedure Rule Committee for their consideration.
No action has been taken.
Paul Marshall, James Christie, Peter Bernard Ladkin, Bev Littlewood,
Stephen Mason, Martin Newby, Jonathan Rogers, Harold Thimbleby, Martyn Thomas
CBE, ‘Recommendations for the probity of computer evidence’, 18 Digital
Evidence and Electronic Signature Law Review (2021) 18-26
https://journals.sas.ac.uk/deeslr/article/view/5240
Articles dealing with the ‘reliability’ of computers
James Christie, ‘The Post Office Horizon IT scandal and the presumption
of the dependability of computer evidence’, 17 Digital Evidence and
Electronic Signature Law Review (2020) 49-70
https://journals.sas.ac.uk/deeslr/article/view/5226
Peter Bernard Ladkin, ‘Robustness of software’ 17 Digital Evidence
and Electronic Signature Law Review (2020) 15-24
https://journals.sas.ac.uk/deeslr/article/view/5171
Peter Bernard Ladkin, Bev Littlewood,
Harold Thimbleby and Martyn Thomas CBE, ‘The Law Commission presumption
concerning the dependability of computer evidence’, 17 Digital Evidence and
Electronic Signature Law Review (2020) 1-14
https://journals.sas.ac.uk/deeslr/article/view/5143
Articles dealing with the consequences when relying on the
‘reliability’ of computers
James Christie, ‘The Post Office IT
scandal – why IT audit is essential for effective corporate governance’, 19 Digital
Evidence and Electronic Signature Law Review
(2022), 42-86
https://journals.sas.ac.uk/deeslr/article/view/5425
Paul Marshall, ‘Scandal at the Post
Office: The Intersection of law, ethics and politics’, 19 Digital Evidence and
Electronic Signature Law Review (2022),
12-28
https://journals.sas.ac.uk/deeslr/article/view/5395
Paul Marshall, ‘The harm that judges do –
misunderstanding computer evidence: Mr Castleton’s story, 17 Digital Evidence and
Electronic Signature Law Review (2020) 25-48
https://journals.sas.ac.uk/deeslr/article/view/5172
Miscarriage of justice and legal advice
Richard Moorhead,
Karen Nokes and Rebecca Helm.
Independent Review, ‘Miscarriages of Justice, and Computer Evidence: Brian
Altman KC’s General Review and the Post Office Scandal’, 20 Digital
Evidence and Electronic Signature Law Review
(2023) 96-19
https://journals.sas.ac.uk/deeslr/article/view/5643
Below is a list of calls for the education of student lawyers, lawyers
and judges, all of which have been ignored:
Editorial, 4 Digital Evidence and Electronic Signature Law Review 2007
Editorial, 7 Digital Evidence and Electronic Signature Law Review 2010
Editorial, 9 Digital Evidence and Electronic Signature Law Review 2012 –
particularly pertinent
Editorial, 10 Digital Evidence and Electronic Signature Law Review 2013
[PLUS a FREE syllabus, https://journals.sas.ac.uk/deeslr/article/view/2017]
I commissioned the following two articles by Denise Wong and Deveral
Capps. Neither were certain that the teaching of electronic evidence was
necessary before they gave the topic any thought, but both agreed it was after
writing their papers. Two elegant essays:
Denise H Wong, ‘Educating for the future: teaching evidence in the
technological age’ 10 Digital Evidence and Electronic Signature Law Review
(2013) 16-24
https://journals.sas.ac.uk/deeslr/article/view/2018
Deveral Capps, ‘Fitting a quart into a pint pot: the legal curriculum
and meeting the requirements of practice’ (2013) 10 Digital Evidence and
Electronic Signature Law Review (2013) 23-28
https://journals.sas.ac.uk/deeslr/article/view/2019
Editorial, 13 Digital Evidence and Electronic Signature Law Review 2016
Editorial, 17 Digital Evidence and Electronic Signature Law Review 2020