The head of a Philadelphia ironworkers union will face a jury alone next month, after three more of his brothers in labor agreed to last-minute plea deals Tuesday, admitting they maintained their local's grip on area construction through violence and sabotage.

Joseph Dougherty - the 72-year-old leader of Ironworkers Local 401 and a man once described as the "Jimmy Hoffa of his local" - has maintained his innocence since he and nine other ironworkers were indicted this year on federal racketeering-conspiracy charges.

But as jury selection began in his case Tuesday, few others were willing to take their chances. All but Dougherty have pleaded guilty to conspiracy, extortion, and other offenses.

The latest batch includes union business agents William O'Donnell and Christopher Prophet, and Richard Ritchie, an up-and-coming ironworker.

Their pleas all hinge on U.S. District Judge Michael Baylson's signing off on a specific sentence worked out between them and the U.S. Attorney's Office.

Baylson cautioned each of the men Tuesday that he could not guarantee his approval until after Dougherty's trial.

Asked why he wanted to plead guilty, O'Donnell said, "To admit the wrongdoing that I did."

While O'Donnell, 62, grew up in a family steeped in the union's culture of brotherhood, plea documents paint the organization as riven with intrigue.

In theory, union members stood together to ensure their collective economic prospects, but wiretapped conversations quoted in court filings depict individual members as driven by individual ambitions and desire to move up in Dougherty's esteem.

Few set their sights higher than the 45-year-old Ritchie, prosecutors said Tuesday. He had joined the union in 1988 and attached himself to Dougherty and Prophet, hoping his willingness to use violent tactics would impress his elders.

He eagerly joined the union's "Shadow Gang," a group run by Prophet, 43, that carried out nighttime sabotage at sites where contractors refused to hire union labor.

Ritchie joined the scrum in 2010 outside a Toys R Us store under construction in King of Prussia, beating nonunion workers with baseball bats. And in a 2013 exchange, he threatened a contractor at a building site at 30th and Market Streets.

Ritchie was also not above a little sucking up to Dougherty. "You're always going to be the Jimmy Hoffa of this local," he told the union chief in a conversation quoted in court filings. "You made this union. You carry this union. You're always going to be this union."

When that approach failed, Ritchie turned to tearing down his colleagues. O'Donnell became one of his favorite targets.

As one of the union's four elected business agents, O'Donnell was charged with ensuring that contractors building in his geographic district hired organized ironworkers.

But despite O'Donnell's overseeing parts of Philadelphia that included work sites with long histories of hiring union members - including oil rigs and the airport - Ritchie deemed him too soft, and often complained to Dougherty about how he could do a better job protecting the union's interests.

Prosecutors, too, described O'Donnell on Tuesday as "by far the least aggressive" of the bunch, and agreed he should receive only a six-month prison sentence, followed by six months of house arrest.

Should Baylson accept their agreements, Prophet's deal would send him to prison for five years, and Ritchie would receive a four-year sentence. Baylson, however, was not so quick to agree that O'Donnell deserved less time.

"I'm doubtful - to be candid - that I'm going to accept this," Baylson said. "I have substantial doubts about accepting this, but I'm going to wait until all the facts are in before making a decision."

Should Baylson reject any of the plea deals, Ritchie, O'Donnell, and Prophet could take their cases to trial.

Dougherty's trial is set to begin Jan. 5.