[SystemSafety] Post Office Horizon System

Peter Bernard Ladkin ladkin at causalis.com
Wed Dec 16 17:26:17 CET 2020

A couple of decades ago, the Post Office introduced a new WAN'd POS called Horizon. Various of its 
franchisees in the early years were accused of fraud; many were prosecuted and convicted; some were 
unable to offer any plausible defence except to say "I didn't do it; really I didn't; there must be 
some mistake".

A class action Bates et al v Post Office was heard in 2019 before Mr. Justice Fraser. Fraser J 
conducted a superb judicial-forensic investigation from the bench, which determined more or less 
that the Horizon system was in fact itself capable of much of the erroneous behaviour which had been 
attributed to franchisee malfeasance in many, possibly even most, of the criminal cases which had 
been prosecuted. Subsequent to Fraser J's ruling, the Criminal Cases Review Commission determined 
quickly that many of the convictions were unsafe.

Some of the problem lies in how UK law treats "electronic"/digital evidence, which includes evidence 
about the behaviour of digital systems. There is a history to this. Barrister Paul Marshall recently 
approached the Ministry of Justice about it. A paper with recommendations on how the law should 
approach this kind of evidence in the future was submitted on request to the Ministry in November 
2020 and a slightly modified version has been published in an open access journal (indirect link below).

Some of us on this list have been involved. I must say I am proud to have been able to help. I am 
sure my colleagues feel the same way. Pro bono publico. There is nothing more rewarding.



Prof. Peter Bernard Ladkin, Bielefeld, Germany
ClaireTheWhiteRabbit RIP
Tel+msg +49 (0)521 880 7319  www.rvs-bi.de

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