The grand jury could decide to indict public or private figures who have been dogged by subpoenas and speculation for years. Or it could end with little tangible progress, as other grand juries investigating this case have, providing a small victory for the mayor and others who have long proclaimed their innocence.
The investigation by the state prosecutor's office began in March 2006, and occasional public disclosures about it have provided clues to the probe's direction, creating bursts of chatter about the prospect of city officials or top developers facing indictment.
Two people connected to Dixon pleaded guilty to tax charges and pledged cooperation. Over the summer, officials from the prosecutor's office spent seven hours searching the mayor's West Baltimore home.
More recently, investigators sought information on Ronald H. Lipscomb, a prominent city developer with close ties to Dixon, whose companies have donated nearly $500,000 to politicians in the past decade. In October, prosecutors subpoenaed thousands of documents related to four city projects awarded to his firm.
The length of the probe has led some to conclude that it turns on complicated evidence. "There is certainly no smoking gun," said David Irwin, a Baltimore attorney who has worked with grand juries for three decades. "That is a generalization of any long, drawn-out investigation."
Describing State Prosecutor Robert A. Rohrbaugh as "excellent" and "aggressive," Irwin said the investigator "wants to satisfy a standard of 'beyond any doubt.'" The fact that numerous grand juries have heard evidence over years "implies to me that there is some doubt," he said.
Frank Anechiarico, a political science professor at Hamilton College in New York who has written extensively on such investigations, described the length of the Baltimore probe as "almost record-breaking."
But public corruption cases are notoriously tricky to build, he said, particularly if the suspected wrongdoing goes beyond one individual.
"If they are going after something more systemic, if that is what they are going after, you should cut them some slack," Anechiarico said. "At the very least, they should be able to flip a few people."
Yet when such cases drag on, he said, there is a danger of undermining public trust in elected leaders. "You think the whole government is rotten," he said. "People tend to think that anyway. I'm not saying that you shouldn't go after someone, but you should do it efficiently."
Once the grand jury expires, Rohrbaugh would need Circuit Court approval to use another panel for the investigation. And, should he not get that, or not seek it, the long-ranging investigation could end.
Rohrbaugh does not confirm or deny that an investigation exists, though his annual reports to the General Assembly include a category for "Baltimore City Investigation." The most recent report noted that two people close to Dixon pleaded guilty to charges and "agreed to cooperate with the state prosectors' continuing investigation."
Rohrbaugh was appointed by then-Gov. Robert L. Ehrlich Jr. in 2004 to a six-year term. His office focuses on investigating violations of public ethics laws, campaign laws and bribery of public officials.
The Baltimore City investigation first came to light in early March 2006 when his office sought subpoenas for city agencies requesting information about work done by Dale G. Clark, Dixon's former campaign chairman.
They were issued shortly after a Sun story revealed that the city paid $600,000 over six years to Clark's firm, Ultimate Network Integration, for supporting the City Council's computer network. He had a contract for only one of those years. In September 2007, Clark pleaded guilty to three counts of failure to file tax returns and is cooperating with a broader investigation.
In late March 2006, Rohrbaugh issued a second set of subpoenas focused on the city's dealings with Union Technologies, or Utech. That came after a series of Sun stories that uncovered that Dixon, who was then City Council president, pressed Comcast representatives in an investigative hearing to send more work to Utech, a small company that employed her sister, Janice Dixon.
Dixon also voted three times on contracts for that company. Ethics rules bar elected officials from using their position to benefit their relatives. In March 2008, Mildred E. Boyer, president of Utech, pleaded guilty to filing a false tax return and is also cooperating.
A November 2007 affidavit from Rohrbaugh's office showed that Dixon received thousands of dollars in gifts, including a $2,000 gift certificate to a local furrier, from Lipscomb, the developer. At the time she was receiving gifts, she voted to award millions of dollars in city work and tax breaks to projects he was working on. Both acknowledged having a personal relationship between 2003 and 2004 and said the gifts had no bearing on the development projects.
The investigation heated up again in June, when investigators raided Dixon's house and hauled out boxes of documents. That development led many to believe that the investigation was wrapping up.
But the summer term grand jury dissolved without indictments and a new one began. In October, the focus seemingly shifted, when the state prosecutor's office issued a new round of subpoenas to the City Council and five city agencies asking for documents about four development projects on which Lipscomb's firm did work. One of them, a proposed gym in East Baltimore, was never completed, though the city and state spent $400,000 for his firm to secure architectural drawings for it.