This story was co-published with PBS Frontline and McClatchy.

WASHINGTON – Waffling by Justice Department lawyers in a wrongful death lawsuit arising from the deadly 2001 anthrax attacks could boost prospects that the government will be liable for millions in damages for failing to prevent the killing of a Florida man.

Department lawyers created a stir in recent days, first by filing court papers that appeared to undercut the FBI's finding that the late Army scientist Bruce Ivins was the killer. The filings said Ivins had no access in a secure lab to the sophisticated equipment to produce the anthrax powder.

Four days later, the lawyers abruptly revised that statement to say he lacked access in his lab to a specific machine that could dry wet anthrax.

“I think it creates a great deal of problems for the government,” said Paul Kemp, who represented Ivins before Ivins' 2008 suicide.

John De Leon, a Miami attorney who is president of the American Civil Liberties Union, said that the legal flip-flop “undermines the government’s credibility” in the civil suit, filed by the family of Robert Stevens, a photo editor for American Media Inc., who was the first of five people to die from the mailed anthrax.

Justice Department spokesman Dean Boyd declined to speculate on what effect, if any, the retraction might have on the ongoing civil litigation. Lawyers for the Stevens family have pursued their case for eight years, but little of the material has come to light until recently. The family is seeking $50 million in damages.

The suit alleges that the strain of anthrax in the letters mailed to three media outlets and two U.S. senators could be traced to a federal bio-weapons research facility at Ft. Detrick, Md., where Ivins worked, and that the laboratory failed to provide adequate security over the storage and handling of anthrax spores.

Using genetic testing on the mailed powder, the FBI says it determined that the spores were descendants of a flask full of anthrax in Ivins’ lab at the facility, the U.S. Army Medical Research Institute for Infectious Diseases.

After a $100 million investigation, the FBI concluded the Ivins had the expertise in anthrax spore production and the means to dry a wet solution into an easily inhaled powder. But the bureau has never produced forensic evidence proving how he made the spores and dried them into a deadly powder.

Kemp, Ivins' former lawyer, noted that the FBI found 116 individuals who might have had access to anthrax emanating from the suspect's flask. Assuming that it indeed originated from that beaker, he said, the Justice Department’s conflicting statements show “that the government has no idea whether it was negligent or not in supervising the maintenance of 150 different pathogens at Ft. Detrick and other locations.”

If the case goes to trial, he said, attorneys for the Stevens family likely will have an opportunity to present the conflicting government statements to a jury.

One way to accomplish that, Kemp said, would be to argue that the department made a “judicial admission” against its own interests last week in stating that Ivins lacked the “specialized equipment” in a secure biocontainment lab, or “hot suite,” to produce the anthrax.

In its revision, the Justice Department contends it was mistaken and that Ivins did have access to the needed equipment—including a machine that could have been used to dry the anthrax spores—elsewhere at the Army facility.

Richard Schuler, the lead attorney for the Stevens family, said he believes that Justice Department lawyers are “trying to pick and choose the facts that will support them in the civil case.

“And in attempting to do that, they’re contradicting their own investigative agency, the FBI.”

He said he presumes that, when officials at the FBI and the Justice Department’s Criminal Division learned of last week’s legal filing, “they were enraged and brought pressure to bear on the civil attorneys to change their submission.”

Now, he said, the civil lawyers are trying “to walk a tightrope of facts in this case in order to attempt to prevent the Stevens family from getting justice.”

If the case proceeds to trial and the Stevens lawyers present a strong case, De Leon said, he believes the jury will “give great weight to the fact that they (government lawyers) are prepared to manipulate the information in the way that they have in this past week.”

The FBI and Justice Department have said Ivins had boasted about his ability to produce highly pure batches of anthrax spores and worked unusually long hours in his lab alone at night in the days prior to the anthrax mailings in September and October of 2001.

Ivins also was the custodian of a specific batch of spores—RMR 1029—that investigators genetically matched to the attack spores, although some of his co-workers say in testimony for the Stevens case that others at Ft. Detrick or even outside visitors could have had access to Ivins’ stock.

In announcing that lawyers for the department’s Civil Division had filed a seven-page correction in federal court in West Palm Beach, Fla., Justice Department Spokesman Boyd stressed that the government has “never wavered from the view that Dr. Ivins mailed the anthrax letters.”

It’s unclear the degree to which the civil suit will turn on Ivins’ role. Earlier this year, the Stevens family opted to withdraw from a stipulation, an agreement by both sides for purposes of the case, that the career anthrax researcher was the perpetrator.

In depositions of former top officials at USAMRIID, Schuler has homed in on the facility’s failure to investigative Ivins’ mental health after he acknowledged receiving psychiatric treatment.

Since the attacks, the government has examined ways to tighten security procedures to better screen for mental health problems among bio-defense researchers.

Contributing: ProPublica intern Aarti Shahani and Research Director Liz Day.