UnitedHealth Group (NYSE: UNH) will go head to head with the U.S. Department of Justice today as the trial regarding its $13 billion acquisition of health care technology company Change Healthcare gets underway.

What's happening: The DOJ has seven days to make its case on what it argues is an anticompetitive deal in nature. UNH-Change gets five days to defend the tie-up they first proposed 19 months ago.

Zoom in: Leading up to the trial, the DOJ has alleged:

• UNH-Change would create a monopoly by marrying Change's EDI clearinghouse and claims editing technology with assets sitting under United's Optum business (ClaimsXten).
• United would gain unfair access to Change’s collection of software and services, now available to various health care players, for itself — along with access to any future innovation.
• The deal would further give UNH access to its rival health insurers’ competitively sensitive data.

The other side: An Optum official told Sarah in February that the company has had access to this kind of data for more than a decade — a fact the complaint ignores, the official said.

• Yes, and: Addressing concerns around the claims editing technology, Change has already agreed to sell ClaimsXten to TPG for $2.2 billion, pending completion of its deal with UNH.
• There are no contingencies that will prevent the ClaimsXten deal from going through if the court approves the UNH-Change merger, a person familiar with the matter says.

The bottom line: The case before a federal judge in Washington, D.C., is the biggest test yet of the Biden administration's antitrust efforts in health care — and could have far-reaching implications for future data M&A plays, our Axios Vitals colleagues write.

Go deeper: Optum plans to fight DOJ