A grand jury has started gathering evidence to determine whether Murphy violated the law when he traded a generous contract with the city firefighters union in return for its endorsement in 2001.
That prosecutors were scrutinizing this deal has long been public knowledge, but the status of the probe and any details remain a secret.
That's always the case with federal investigations, in which prosecutors, agents and grand jurors are under strict rules not to reveal information -- or even acknowledge that an investigation is under way.
Those on the outside, then, are only left to speculate about what might be going on. Here is what is known:
On April 12, fire union chief Joseph King issued a letter saying Murphy traded $10 million to $12 million in fire union contract demands, including no-layoff protections, in exchange for the union's votes in the 2001 primary. After the district attorney and the U.S. attorney promised to investigate, the FBI started interviewing witnesses in May, including King, Murphy and his top aide, Tom Cox.
Then, last month, city Solicitor Jacqueline Morrow delivered documents related to the contract that had been subpoenaed by a grand jury under the direction of First Assistant U.S. Attorney Robert Cessar.
Cessar will likely summarize those records for the grand jury, one of five that hear cases in U.S. District Court, at a future session. Federal grand juries usually meet once a month, and unlike state or county panels convened for a special purpose, they hear all manner of cases for 18 months.
The grand jury has the power to subpoena all records and witnesses, but in this case apparently no one has yet been called to testify. The fact that Murphy has hired a lawyer, Robert Del Greco Jr., does not mean he's going to be charged. It's normal practice for everyone involved in grand jury proceedings to hire lawyers, who aren't allowed in the grand jury room but can advise their clients outside. The law was used to convict former state Rep. Frank Gigliotti and former Allegheny County Common Pleas Judge Joseph Jaffe, among others.