Taiwan prosecutors have charged 14 people over insider trading in Optimax (力特光電) shares before the company sold its Tainan science-park plant to TSMC — bad news for the defendants, and a reminder that family dinner talk can be a crime.

• Optimax tried to auction the plant in 2019 but the pandemic delayed the sale, and TSMC eventually bought it for less than the asking price.
• The chairwoman mentioned the deal to her son at a weekend family gathering; her daughter and daughter-in-law overheard and passed it to relatives, who bought shares the day before the announcement.
• A general affairs manager handling the plant shutdown also bought a large block of stock and tipped off a brother-in-law; several other staff did the same.
• Eleven of the accused have already returned their profits, which they hope will earn lighter sentences.
• The chairwoman and her son were not charged, since prosecutors accepted they had no idea relatives would trade on the chat.

Outlook: The case now goes to trial in Taipei, where the returned profits will likely shape sentencing more than guilt.