How can you follow along with a grand jury process when the whole thing is secret? Ask a white-collar defense lawyer.

Special counsel Robert Mueller has convened a grand jury to investigate Russian interference in the 2016 election and possible collusion with President Donald Trump's presidential campaign, according to a new report from The Wall Street Journal Thursday. According to Reuters, that grand jury has issued subpoenas related to a meeting between Trump's son, Donald Trump Jr. and a Russian lawyer last year.

The news indicates that Mueller and his team of 16 lawyers are now issuing subpoenas and may also call witnesses to testify under oath, if they haven't already. The grand jury is in Washington, D.C., and began its work in the past few weeks, the Journal report said.

A grand jury investigation is secret. Neither jury members, prosecutors or agents involved are allowed to discuss it. So what's important to watch and know as the process unfolds? Here's what white-collar lawyers say:

Mueller has reached a new level. The role of a grand jury is to listen to evidence brought by federal prosecutors and, when the time comes, decide whether to issue an indictment. The fact Mueller has turned to the grand jury process, which allows him to issue subpoenas for a broad range of documents, means his investigation has reached a different level, said Perkins Coie partner Barak Cohen. Cohen is a former federal prosecutor who chairs the firm's Washington, D.C., commercial litigation practice.

“Prosecutors don't just open grand juries,” Cohen said. “This should tell you that Mueller now has enough evidence of a crime having been committed.There's enough evidence to open a grand jury.”

It's about to get leaky. The only people who can legally talk about what happens in the room during a grand jury investigation are the witnesses. But William Jeffress, a partner at Baker Botts who defends corporations and individuals in federal criminal proceedings, said information can get out other ways, too. A witness could tell a friend about the experience, and the friend could leak the information. A defense lawyer for a witness could say something offhand.

“Leaks are coming,” Jeffress said.

Another option? Reporters can loiter around the federal courthouse in D.C. and report on comings and goings. But the grand jury can meet sporadically, so there's no way to know for sure when it's meeting.

“There's a reason why reporters are always waiting [around the courthouse],” Cohen said.

Who is getting subpoenaed? Who are the witnesses? During a grand jury investigation, prosecutors can issue subpoenas for a wide range of documents, explained former federal prosecutor Jason Jones, now a partner in King & Spalding's special matters and investigations practice. The subpoenas and documents that follow, like the entire investigation, are secret. But again, those on the receiving end can talk about them.

Jeffress said documents are one thing, but it gets interesting once Mueller starts calling witnesses to testify under oath.

“Issuing subpoenas for documents means very little,” Jeffress said. “It just means they've concluded they need the law to get documents. When they start issuing subpoenas for testimony, it means they're serious.”

Watch for subpoena battles. When someone receives a subpoena, they can fight it if they don't want to comply, Jones said.

Why wouldn't someone comply? Maybe they think the request violates their Fourth Amendment right to privacy or that it's beyond the scope of Mueller's inquiry. Fighting the subpoena would involve filing a motion with a district court judge in D.C. Those motions would likely be redacted, but again, leakers may point out when such a fight is ongoing.

What about immunity? Pay attention if there's news a witness was granted immunity.