Elon Musk’s lawyers have sent a subpoena to Jack Dorsey, the first indication that Twitter’s co-founder and former chief executive will be officially involved in the legal fight over Musk’s stalled $44bn deal.

Musk is seeking documents from Dorsey relating to the effect of false or spam accounts on the social media platform’s business. The Tesla CEO is also seeking information about Twitter’s use of monetisable daily active users, or MDAUs, as an important metric and any other metrics the company might use to describe user or advertiser engagement.