In the Twitter takeover dispute, high-tech billionaire Elon Musk is also relying on information from the former security chief of the short message service, who recently accused his former employer of covering up security gaps.
Musk asked Peiter Zatko to hand over documents about spam or fake accounts on Twitter, according to court documents released on Monday.
Zatko was also asked to answer questions from the lawyers of the boss of the electric car manufacturer Tesla in September.
Zatko's lawyers told the AFP news agency that their client would comply with the requests.
However, his statements to Musk's lawyers would be "involuntary".
In a recent report to the US Securities and Exchange Commission, the Justice Department and the US Competition Authority, Zatko spoke of “serious and shocking vulnerabilities” on Twitter.
There is talk of outdated servers, vulnerable operating systems and executives who have covered up a series of hacks into Twitter data.
Zatko also accuses his former employer of misrepresenting the number of users - an accusation that Musk wants to use in the legal dispute with Twitter.
The richest person in the world and the short message service are currently in a bitter legal battle after Musk canceled an initially planned takeover of Twitter.
The actual trial begins on October 17 in a specialized court in the state of Delaware on the US east coast.
Musk announced a $44 billion takeover of Twitter in April.
In early July, however, Musk dropped the deal because of allegedly "false and misleading" information from the short message service.
The background is the number of spam or fake accounts on Twitter.
Musk accuses the platform of overestimating the actual number of users.
Twitter has denied the allegations and insists that Musk complete the takeover.
Meanwhile, according to a report in the Tagesspiegel newspaper, the billionaire arrived in Berlin on Monday evening to get an idea of Tesla's Gigafactory ramping up.
It is the Tesla boss's first visit since the factory opened in March.