SAN FRANCISCO — Three years after his death, Steve Jobs is very much a presence in courtrooms across the country.

And that’s not necessarily good news for Apple.

In December, the company is set to go to trial in the third major antitrust lawsuit it has faced since Mr. Jobs died. His emails will play an important role in the case, as they did in the last two. But lawyers will probably have to work hard to give his statements a positive spin. The potential damages — around $350 million — are a pittance for a company that in its last quarter had an $8.5 billion profit.

Executives are often told by their lawyers to be careful what they put in writing for fear it will end up as evidence in a courtroom. Perhaps Mr. Jobs did not get the memo. His emails in past lawsuits — a mix of blunt litigation threats against his opponents and cheery financial promises for potential business partners — have made him an exceptional witness against his own company, even beyond the grave.

The emails in all these cases present the good and bad of Steve Jobs — charmer and bully, someone who may not always have played by the rules.