Photo/Illutration Greg Kelly, left, a former director of Nissan Motor Co., enters the Tokyo District Court on March 3. (Pool)

A court ruling concerning financial misconduct at Nissan Motor Co. underscores the risks that prosecutors take in relying on testimony from a witness under a plea bargaining deal.

Toshiaki Onuma, the former head of the secretary’s office at Nissan, agreed to testify at the trial of former Nissan Director Greg Kelly in exchange for immunity from indictment.

The plea bargaining system has been used three times since it started in Japan in June 2018. The Kelly trial, concerning the suspected concealing of remuneration by Carlos Ghosn, the former Nissan chairman, was the most well-known of the three plea bargaining instances.

But the Tokyo District Court said it would accept Onuma’s testimony only if other evidence or witness corroboration backed what he said.

Onuma did not help himself when his testimony in court did not completely match what he had said during initial questioning by prosecutors investigating the case.

The discrepancies revolved around when he showed Kelly an agreement written in 2011 on how to underreport Ghosn’s remuneration.

The March 3 ruling said about Onuma’s testimony, “There were many doubts about what he said.” And with nothing to support his claims, his testimony was deemed unreliable.

That in part led the court to rule that Kelly was unaware of the underreporting for the years between 2010 and 2016.

The court only found Kelly guilty for 2017 because there was a file marked “Kelly” containing documents related to the underreporting.

Onuma testified that he gave the file to Kelly, and an Onuma associate backed that assertion in the trial.

Kelly was found guilty for only that one year, and the court gave him a six-month prison sentence, suspended for three years.

The latest ruling follows the wording used by other courts regarding cases involving plea bargaining.

Those courts also said there was a need for special care when evaluating the words of individuals who have agreed to testify in exchange for immunity.

(This article was written by Kazufumi Kaneko and Wataru Netsu.)