Japanese fund manager Yoshiaki Murakami has pleaded not guilty to insider trading charges in a trial involving scandal-hit internet firm Livedoor.
The scandal around Mr Murakami's fund has had wide implications
In June, Mr Murakami was indicted for getting confidential data from Takafumi Horie, Livedoor's ex-chief executive.
Now a key witness from Livedoor says Mr Murakami bought Nippon Broadcasting shares, aware that Mr Horie would later buy a large share in the radio firm.
The case has had a big impact in Japan, reaching as far as the Bank of Japan.
The central bank's governor, Fukui Toshihiko, had invested 10m yen (£43,000; $85,000) in Mr Murakami's fund, MAC asset management, before his appointment as head of the bank.
Once news of his investment in the fund run by Mr Murakami - a former government bureaucrat - was made public, Mr Fukui faced pressure to renounce his high-profile position.
The trial's latest stage has focused on claims from key witness Ryoji Miyauchi, Livedoor's former financial officer.
He told prosecutors of how Mr Horie and Mr Murakami discussed plans that would enable Livedoor to ultimately acquire Nippon Broadcasting.
Livedoor planned to buy about a third of Nippon Broadcasting, which, when added to MAC's 18%, would give them majority control of Nippon Broadcasting, said Mr Miyauchi.
Owning a significant share in Nippon would, in turn, give Livedoor major control over media company Fuji Television - something Mr Horie had long wanted, said Mr Miyauchi.
Mr Murakami has rejected charges that he bought Nippon shares based on knowledge of Livedoor's future plans.
Livedoor went on to buy a 35% share of Nippon in February 2005.
Mr Horie, like Mr Murakami, has pleaded not guilty.
MAC was said to have made about 3bn yen ($25.9m; £13m) after buying Nippon shares, prosecutors said.
Mr Murakami could face up to five years in prison as well as a 5m yen fine.
In separate charges regarding Livedoor, Mr Horie has been arrested for accounting fraud for falsely reporting profits in 2004 in a bid to hide huge losses.