(AP) — Elon Musk’s legal team is demanding to hear from Twitter’s whistleblowing former security chief, who could help bolster Musk’s case for backing out of a $44 billion deal to buy the social media company.

Former Twitter executive Peiter Zatko — also known by his hacker handle “Mudge” — received a subpoena Saturday from Musk’s team, according to Zatko’s lawyer and court records.

The billionaire Tesla CEO has spent months alleging that the company he agreed to acquire undercounted its fake and spam accounts — and that he shouldn’t have to consummate the deal as a result.

Zatko’s whistleblower complaint to U.S. officials alleging Twitter misled regulators about its privacy and security protections — and its ability to detect and root out fake accounts — might play into Musk’s hands in an upcoming trial scheduled for Oct. 17 in Delaware.

Zatko served as Twitter’s head of security until he was fired early this year.