Hironaka told the briefing that prosecutors were acting in a “cruel way” and putting him under intense physical and mental pressure to get a confession.
Prosecutors were not immediately available for comment.
Hironaka has previously criticised the move by prosecutors to confiscate Ghosn’s belongings, including his mobile phone and trial documents, along with the mobile phones and Lebanese passport of his wife, Carole, who was present when prosecutors entered their home early in the morning last Thursday.
The lawyer said on Tuesday that Ghosn’s wife, who left Japan last week, did so out of concern for her own safety, adding she intended to protest the case to the French government.
However, France’s finance minister said on Tuesday that political interventions might not be the best way to help Ghosn, raising some questions about how much pressure Paris was willing to put on Tokyo over the issue.
The case has rocked the global auto industry and also shone a harsh light on Japan’s judicial system.
Under Japanese law, prosecutors are able to hold suspects for up to 22 days without charge and interrogate them without their lawyers present.
Such procedures have focused much attention in the West on Japan’s judicial system, which critics sometimes refer to as “hostage justice”, because defendants who deny their charges are often not granted bail.
Ghosn has been charged with under-reporting his Nissan salary for a decade, and of temporarily transferring personal financial losses to Nissan’s books. However, the new, $5 million allegation is potentially more serious, as it could show he used company funds for his own purposes.
On Monday, Nissan shareholders ousted him as a director, severing his last tie with the automaker he rescued from near-bankruptcy two decades ago.