On the opening day of what is likely to be the most consequential antitrust showdown in decades, a federal judge contemplated how to evaluate whether tools of the modern workplace, like email chains, can be used as evidence against AT&T.

District Judge Richard Leon of the District of Columbia, who is overseeing the Justice Department’s lawsuit against AT&T’s proposed merger with Time Warner, said in Monday’s evidentiary hearing that there were a couple of overarching issues in AT&T’s objections to the government’s evidence, including many focused on relevancy. But one was also whether certain types of evidence, such as emails, counted as business records exempt from court rules against hearsay evidence.