The Atlanta Journal Constitution reports that the grand jury investigation into Rep. Cynthia McKinney’s alleged assault on a Capitol Hill police officer is now in month three. (Hat tip: Lucianne.com)

The message sent to Capitol Hill cops is clear:

“Right from the start this U.S. attorney has handled this case differently from every other case,” said Chuck Canterbury, national president of the Fraternal Order of Police. “And it’s because she is a sitting congresswoman.”

McKinney’s office and the office of U.S. Attorney Ken Wainstein declined to comment.

The case comes at a time of heightened tensions in Washington. A series of arrests, indictments and criminal investigations involving at least five members of Congress have fueled disputes between Capitol police and Congress and between Capitol Hill and the Justice Department.

Republicans and Democrats alike furiously denounced a recent FBI raid on the office of Rep. William Jefferson (D-La.) as a violation of the constitutional separation of powers.

And Capitol police, already angry over McKinney’s case, bristled when superiors ordered them last month to drive Rep. Patrick Kennedy (D-R.I.) home rather than investigate the possibility that he’d been drinking after he crashed his car into a barricade near the Capitol. Kennedy later blamed the incident on prescription drugs he’d been taking and checked into a rehabilitation facility.

What most angers the police about the McKinney case is that it involves an assault — no matter how minor — of a police officer. Police reported that McKinney hit an officer in the chest after he failed to recognize her as a member of Congress and tried to stop her from going around a security checkpoint, something members of Congress and their aides are typically allowed to do.

“It’s obviously frustrating for us,” said Andy Maybo, head of the Capitol Hill police union. “This sends out the message that it’s OK to hit a police officer — and it’s not, regardless of who you are.”

McKinney and staff refuse to talk about the incident anymore. The strategy seems to be working. AP says many of her constituents are backing her…“150 percent.”