The flaw in Fujitsu's accounting software that led to the court's wrongful conviction was known to both companies "from the beginning"

A Fujitsu executive has admitted that a flaw in the company's Horizon accounting software led to the conviction of nearly a thousand British post office workers for theft or fraud, and that the error was known to both companies from the start. The scandal has jailed some workers and been linked to at least four suicides.

In 1999, Fujitsu subsidiary International Computer Co., Ltd. installed a Horizon software system at the British Post Office. As of 2015, more than 900 deputy postmasters and postmasters were prosecuted and convicted on charges of theft and false accounting after money was missing from their branches. The "Horizon", which was covered with bugs, was used as evidence for the prosecution.

Some people who were wrongly accused were sent to prison. Many victims face financial ruin and have their lives and relationships unraveled after being forced to pay back money that was never stolen and huge legal fees. It is understood that four of the wrongly accused committed suicide.

The British Broadcasting Corporation (BBC) wrote that more than 20 years later, only 93 convictions have been overturned, and thousands of people are still waiting for compensation.

Paul Patterson, co-chief executive of Fujitsu Europe, said: "As part of a public investigation into Fujitsu's reluctance to let the Post Office know about Horizon's flaws, all the vulnerabilities and errors have been known to a greater or lesser degree many, many years ago. There were vulnerabilities, errors and flaws that were known to all parties from the beginning of the system's deployment."

Patterson said it was "shameful and shocking" that the court had not been informed of the 29 vulnerabilities in the Horizon system, despite them being discovered as early as 1999.

When the Horizon vulnerability was identified, witness statements from Fujitsu employees were edited by Postal Service lawyers to appear as if the system was operating without any problems, continuing to assist in the prosecution of innocent workers. Patterson added that in some witness statements, Fujitsu failed to detail many of Horizon's problems and that the "vast majority" of bugs, errors and defects were shared with the post office.

"I was surprised that this detail was not included in the witness statements provided to the Post Office by Fujitsu employees, and I have also seen some evidence of others redacting witness statements," Patterson said. "When asked if he thought this behavior by the company was disgraceful, the executive said: 'I would use that word.'"

Fujitsu is under pressure to pay £1 billion ($1.2 billion) in victim compensation earmarked for British government ministers. Patterson said the Japanese company was sincerely sorry for its role in the "appalling miscarriage of justice" and that it had a "moral obligation" to provide compensation to those affected.

The Post Office has been asked by the government to review its previous accounting system, Capture, which also led to wrongful convictions after previous potential miscarriages of justice were revealed.

Fujitsu Chief Executive Takahito Tokita declined to confirm whether the company would return any money it earned from Horizon.