Whitey Bulger to face 'The Rifleman,' his right-hand man, in court

Stephen 'The Rifleman' Flemmi is expected to testify in the James 'Whitey' Bulger case Thursday. As Bulger's former partner in crime, Flemmi could be crucial to the prosecution.

The trial of Boston crime boss James "Whitey" Bulger is nearing a pivotal moment, as the prosecution tries to cement its case by calling his former partner to testify.

Stephen "The Rifelman" Flemmi is expected to take the witness stand Thursday and to say that he and Mr. Bulger cooperated in killings that included two women.

Bulger was captured in 2011 after a 16-year manhunt. Federal prosecutors say Bulger ran an organized-crime outfit with Mr. Flemmi that was responsible for extortion and at least 19 murders. Flemmi, who is serving a life prison sentence after admitting to 10 murders, is central to their case.

Although Bulger has pleaded not guilty, his defense lawyers have acknowledged that their client was deeply involved in criminal activities such as gambling and loan sharking. But the defense attorneys are seeking to cast doubt on the credibility of key prosecution witnesses – including Flemmi and other former criminals who received lighter sentences in return for their willingness to testify.

Topping Bulger’s wish list, according to news reports, is to cast doubt on the notion that he served as an FBI informant or that he killed women.

Flemmi’s testimony promises to go to the heart of both issues.

A 700-page FBI file documenting Bulger as an informant is based on numerous meetings between Flemmi, Bulger, and FBI Agent John Connolly, prosecutors say. Bulger’s attorneys say, rather, that their client was paying Mr. Connolly for information and protection, not giving the FBI tips.

And Flemmi testified in a 2009 court case that he and Bulger cooperated in the 1980s to kill Debra Davis and Deborah Hussey – two of the 19 murder victims whose killings are included the federal case against Bulger.

When Flemmi gave that testimony, he may have doubted whether he would ever see his former crime partner again. Bulger at the time was listed among the FBI’s "Most Wanted" as he set up a secret new life with a longtime girlfriend, under pseudonyms, in a California apartment.

Since the trial started in June, Bulger has at times erupted in profanity at prosecution witnesses.

That, coupled with the replies that witnesses have sometimes directed back at the defendant, has prompted Judge Denise Casper to issue stern reminders of courtroom protocol.

Flemmi’s nickname came from his military service in the Korean War, but it fit the brutal underworld realm in which he operated.

Ms. Davis was a Flemmi girlfriend, and Ms. Hussey was a stepdaughter. Flemmi has said both were killed at Bulger’s insistence, and by Bulger’s strangling, because of the risk that dark secrets they knew might leak out.

Earlier in the current trial, former Bulger associate Kevin Weeks testified that he also witnessed one of the murders, that of Hussey.

If Bulger takes the witness stand for his own defense, a jury and the public may hear his version of events for the first time.

The prosecution part of the case is nearing its end. Bulger’s attorneys this week released a pared-down witness list.