"I don't think it means a lot about the substance of the case," he said. "It's more about the process."
Generally, Cassell explained, recusals occur if "the subjects of the investigation are deemed to have a connection to the U.S. attorney's office … that would make it wise to bring an unbiased set of eyes in from out of town."
This latest development in the Swallow saga comes days after indicted St. George businessman Jeremy Johnson accused Assistant U.S. Attorney for Utah Brent Ward of trying to protect Swallow from possible criminal charges even as federal officers were investigating the state lawman.
Ward, Johnson alleges, had offered to provide immunity to Swallow as a part of a plea deal with Johnson. That agreement later unraveled.
Swallow's attorney, Rod Snow, said Monday the recusal's timing may have been tied to Johnson's allegations against Ward, but he added that the businessman's latest barrage is "about as credible as any of the allegations Johnson has made, which is not credible."
Snow said the change is "unfortunate, in the sense it may cause additional delay" in wrapping up the investigation.
He also said his "sense of the investigation is that it's broader than what any of us realize."
"I don't think Swallow is the focus of it," Snow added. "In other words, I think it may be broader or have expanded."
The attorney declined to say why he believes that.
Melodie Rydalch, spokeswoman for the U.S. Attorney's Office in Utah, said the decision to have the office remove itself from the case came in consultation with Justice Department officials in Washington.
"It is not uncommon for offices to recuse," she said. "It's a standard practice."
The most prominent example of such a recusal came when the Utah office stepped aside from the Salt Lake City Olympic bribery scandal investigation and prosecution due to potential conflicts within the office. That probe and prosecution went to lawyers in the Public Integrity Section, as well, and ultimately led to the acquittal of two Olympic organizers.
Swallow had requested the federal probe after Johnson revealed that Swallow, then Utah's chief deputy attorney general, had sought to help Johnson deal with a Federal Trade Commission investigation of Johnson's I Works business.
Swallow has said he put the Utah entrepreneur in touch with the late Richard Rawle, founder of the Provo-based Check City payday-loan chain, to hire a lobbyist for Johnson.
Johnson said he paid Rawle as part of what Johnson has insisted was a scheme to bribe Senate Majority Leader Harry Reid, D-Nev.
"During the course of the investigation, with my interactions with the FBI," said Snow, "they have indicated Swallow is a witness in their investigation regarding Johnson's allegations about Harry Reid. They've never identified him as a subject or a target."
Reid, like Swallow, has denied Johnson's allegations.
Former Utah Attorney General Mark Shurtleff has said he went to federal investigators months before Johnson's allegations surfaced after learning of Swallow's deal with the businessman.
The FBI has also interviewed several business owners who allege that Swallow told them that making contributions to Shurtleff could be beneficial if their businesses became targets of investigations.
Tribune reporter Tom Harvey contributed to this story.
The Swallow probe
Indicted St. George businessman Jeremy Johnson, who faces 86 criminal counts, has alleged that Utah's attorney general, John Swallow, helped broker payoffs to enlist the aid of Senate Majority Leader Harry Reid in derailing a Federal Trade Commission investigation of Johnson's I Works business.
Swallow and Reid have denied the allegations. The Justice Department's Public Integrity Section is investigating.