In the early-morning hours of Sept. 8, Dan Rather was preparing to fly to Washington for a crucial interview in the Old Executive Office Building, but torrential rain kept him in New York.

White House communications director Dan Bartlett had agreed to talk to "60 Minutes," but only on condition that the CBS program provide copies of what were being billed as newly unearthed memos indicating that President Bush had received preferential treatment in the National Guard. The papers were hand-delivered at 7:45 a.m. CBS correspondent John Roberts, filling in for Rather, sat down with Bartlett at 11:15.

Half an hour later, Roberts called "60 Minutes" producer Mary Mapes with word that Bartlett was not challenging the authenticity of the documents. Mapes told her bosses, who were so relieved that they cut from Rather's story an interview with a handwriting expert who had examined the memos.

At that point, said "60 Minutes" executive Josh Howard, "we completely abandoned the process of authenticating the documents. Obviously, looking back on it, that was a mistake. We stopped questioning ourselves. I suppose you could say we let our guard down."

CBS aired the story eight hours later, triggering an onslaught of criticism that has left Rather and top network officials struggling to explain why they relied on a handful of papers that even some of Rather's colleagues now believe to be fake.

An examination of the process that led to the broadcast, based on interviews with the participants and more than 20 independent analysts, shows that CBS rushed the story onto the air while ignoring the advice of its own outside experts, and used as corroborating witnesses people who had no firsthand knowledge of the documents. As CBS pushed to finish its report, it was Bartlett who contacted the network -- rather than the other way around -- at 5:30 the evening before to ask whether the White House could respond to the widely rumored story.

Later, Bartlett would explain why he did not challenge the documents with a question: "How am I supposed to verify something that came from a dead man in three hours?"

Other questions abound: How could a program with the sterling reputation of "60 Minutes," which created the television newsmagazine during the Johnson administration, have stumbled so badly? And how could Rather, at 72 the dean of the network anchors, have risked his reputation on such a story in the heat of a presidential campaign?

CBS News President Andrew Heyward, who joined the network 23 years ago as Rather's producer, said his staff was extremely careful with the story. "We have a thorough vetting process," Heyward said last week. "Everyone was aware this was a high-stakes story." He approved the piece, Heyward said, because "we felt it was ready."

Rather also dismissed the notion that CBS was negligent: "I'm confident we worked longer, dug deeper and worked harder than almost anybody in American journalism does."

The Mother Lode

Mary Mapes had been trying to get her hands on the rumored documents for five years.

The Dallas-based producer, known for staying calm when everyone else is agitated, goes back a long way with Rather. In 1999, a judge ordered her jailed for refusing to turn over transcripts of Rather's interview with a man accused in the dragging death of James Byrd Jr. -- but she was spared when CBS finally surrendered the papers. When Rather broke the story of Iraqi prisoner abuse at Abu Ghraib this spring, it was Mapes who helped obtain the shocking pictures.

In mid-August, Mapes told her bosses that she had finally tracked down a source who claimed to have access to memos written in 1972 and 1973 by the late Lt. Col. Jerry B. Killian, Bush's squadron commander in the Texas Air National Guard. The memos, she was told, revealed how the young pilot from a famous family had received favorable treatment, even after refusing an order to report for a physical. Rather and his producer met the source at an out-of-the-way location.

Mapes, an associate producer and a researcher were carrying the journalistic load. "The show is not so lavishly budgeted that we have tons of people doing this," said Harry Moses, a "60 Minutes" producer not connected to the story. "You do the pre-interviews yourself and then bring in the correspondent."

During the Republican National Convention in New York, Rather got a call from Ben Barnes, a onetime Texas lieutenant governor and veteran Democrat who has known the anchor, a former Houston TV reporter, for 30 years. Barnes said he was ready to say before the cameras that he had pulled strings to get Bush a coveted slot in the Texas Guard in 1968. Mapes had long been urging Barnes to tell his story.

On Friday, Sept. 3, the day after the convention ended, Mapes hit pay dirt. She told Howard her source had given her the documents. Within hours, Mapes began calling around to find independent analysts who could examine the handful of memos said to have been written by Killian. She found one in Dallas, who helped put her in touch with three others.

The next stop was Texas. Rather was in Florida, so CBS chartered a plane to get him to Austin. On Sunday, Sept. 5, he and Mapes interviewed Robert Strong, an administrative assistant in the Texas Guard during Bush's service there. Strong told them the memos were compatible with what he knew of Killian but did not claim to have seen them before. "I cannot recall that Jerry Killian talked about Bush, and am not sure he would have discussed it with me," Strong recently told The Washington Post.

That same day, back in the ninth-floor offices of "60 Minutes," across West 57th Street from the CBS Broadcast Center, warnings about the story began to surface.

Expert Opinions

Emily Will of North Carolina, one of the experts CBS had asked to examine the memos, sent Mapes an e-mail outlining her concerns over discrepancies in Killian's signature. She also phoned CBS and raised more questions about whether the typography in the memos existed in 1972 and differences with other military documents. "They looked like trouble to me," Will said.

Linda James, a document examiner who lives near Mapes, was raising similar questions. The two memos she looked at "had problems," James recalled telling CBS, and she could not rule out that they had been "produced on a computer."

Document analyst Marcel Matley flew from California to New York, and Rather interviewed him on Labor Day, Sept. 6 -- footage that would end up on the cutting-room floor. But Matley limited his examination to Killian's signature, which he believed was probably valid, but not certain -- the lowest endorsement he offers. Because the memos were copies, Matley said in a recent interview, "there's no way that I, as a document expert, can authenticate them. . . . I can't say either way from my expertise, the narrow, narrow little field of my expertise."

None of the analysts, including the fourth, James J. Pierce of California, provided the network with a written report before the broadcast. Howard said Mapes told him the analysts' concerns had been addressed.

Rather said he grew more confident when Mapes began speaking with retired Col. Bobby W. Hodges, Killian's superior in the Guard. Hodges said Killian felt that Bush had been treated too leniently in those days. That was important, in Rather's view, because Hodges remained a staunch supporter of the president. But Hodges later said that he felt "misled" by CBS, that the memos were read to him over the phone and that he believes from discrepancies in the military abbreviations that they are forgeries.

On Tuesday, Sept. 7, as Rather sat down in a CBS studio with former Texas lieutenant governor Barnes, the top brass was turning its attention to the explosive story. Heyward, the news division chief, met with Senior Vice President Betsy West; executive producer Howard, who had taken over in June after shifting from the program's Sunday edition; Mapes; senior broadcast producer Mary Murphy; and Esther Kartiganer, whose job is to ensure that interviews are not edited in a misleading way.

"All of us asked questions," Heyward said.

"We asked core questions -- about reliability, authenticity, motivation, could the source have had access to the documents," West said. The executives were satisfied by Mapes's answers, and she began writing the script.

But in separate phone calls to Mapes that day, two of the network's outside experts tried to stop the journalistic train, or at least slow it down.

Linda James said she "cautioned" CBS "if they ran it, that the problems I saw, that other document examiners would see. It just wasn't ready. The package wasn't ready. It didn't meet authenticating [standards]. To go at that stage, I just couldn't imagine."

Emily Will said she called the network that Tuesday and repeated her objections as strongly as possible. "If you air the program on Wednesday," she recalled saying, "on Thursday you're going to have hundreds of document examiners raising the same questions."

Howard said "60 Minutes" had planned to call Bartlett for an interview when the Texas-born Bush aide contacted CBS first on Tuesday evening. Back in his Manhattan apartment that night, at 11 o'clock, Howard got an e-mailed version of the script from Mapes. He sent it back with suggestions. The next morning -- which loomed as deadline day -- he got up at 6 to look at a revised version.

Rather was already at the studio, recording the audio track. At 11 a.m., Howard, West, Murphy and Kartiganer gathered to watch another piece in the screening room, where they were joined by two CBS lawyers as they began discussing the Guard story. Howard had a backup segment planned -- "60 Minutes" was still in rerun season -- in case he decided to hold the Rather story. Mapes left the meeting to take John Roberts's call from the White House.

Bartlett said he caught the president leaving for a campaign trip that morning and showed him the memos. Bush had "no recollection of having seen them," Bartlett said, and would not necessarily have seen papers from a commander's personal file.

Howard was struck by the fact that Bartlett, in his interview, kept referring to the Killian memos to support his argument that the president had fulfilled his military obligations.

"This gave us such a sense of security at that moment that we had the story," Howard said. "We gave the documents to the White House to say, 'Wave us off this if we're wrong.' " But Bartlett said CBS never asked him to verify the memos and that he had neither the time nor the resources to do so.

The wheels were in motion. In mid-afternoon, the CBS executives went into a pair of eighth-floor editing rooms where the segment was being put together in pieces, over Rather's soundtrack. They made some script changes as the crew struggled to slice three minutes out of the 15-minute segment.

At 7 p.m., Heyward joined the other executives in the Broadcast Center screening room for a final look at the piece as it was being fed into the show. He could still raise objections, but it would be difficult to make major changes with the clock ticking like the famed "60 Minutes" stopwatch. No changes were made.

Forty-five minutes later, 8.1 million people watched Rather report that Bush had received preferential treatment in the Guard. The program rated second, finishing behind the NBC drama "Hawaii."

After the show, one colleague asked an elated Rather whether he was sure the documents were real. "I have never been more confident of a story in my life," he said.

Typing and 'th's

The first sign of trouble came the next afternoon, when a staffer told Howard that a Web site was questioning whether the Killian memos could have been produced on an early 1970s typewriter. In fact, the Internet was buzzing with such critiques. Howard asked Mapes about one of the charges, that typewriters of that period did not use superscripts, such as a raised "th," that appeared in the memos. She came back with military documents that used a small "th," but the letter combination was not raised above the rest of the type, as true superscript would be. Howard said he believed some of the outsiders' questions about superscript and proportionate spacing were "kind of silly."

On Friday, Sept. 10, as major news organizations began questioning the validity of the memos, Rather interviewed document expert Matley by satellite from San Francisco and used his comments on the "CBS Evening News." In the piece, Rather strongly defended the network's story, even while noting that "some people, including many who are partisan political operatives," were questioning whether the documents were authentic. Rather, who had first tangled with a Republican White House during Watergate, said in an interview that the focus should not be on CBS and that journalists "should be asking President Bush and his staff questions about what is true and not true about the president's military service."

A new problem surfaced when reporters found that the man cited in a 1973 memo as pushing to "sugarcoat" Bush's record, Col. Walter B. "Buck" Staudt, had been honorably discharged a year and a half earlier.

On Monday, CBS turned to two new analysts to counter the critics. One of them, Richard Katz, said later that he had merely set out to prove the memos had not been created with Microsoft Word or other modern computer programs. He told The Post that he is not a document examiner and that "I have no interest in authenticating the documents." The other analyst, Bill Glennon, said he is an information technology consultant, adding: "I'm not an expert, and I don't pretend to be."

Pierce, the California analyst first consulted by CBS before the broadcast, gave the network a three-paragraph statement calling the memos "strongly similar to corresponding samples," but CBS did not release any corroborating evidence.

Rather defended the story again on the evening news that night. But this time, he said, "some of these questions come from people who are not active political partisans." He closed by saying that CBS "believes the documents are authentic."

Asked at the time whether there was at least a slight chance that the documents were bogus, Heyward said: "I see no percentage of possibility."

A Telltale Sign

It quickly became clear that the people CBS hired to authenticate the documents had -- and claimed -- only limited expertise in the sometimes arcane science of computer typesetting technology and fonts. Such expertise is needed to determine whether the records could have been created in 1972 and 1973. Independent experts contacted by The Post were surprised that CBS hired analysts who were not certified by the American Board of Forensic Document Examiners, considered the gold standard in the field.

These software experts say differences in font widths and printing styles make it impossible to replicate the CBS documents using the printing technology available in the early 1970s. By contrast, reasonably competent computer enthusiasts have created nearly exact replicas of the documents in 15 minutes employing default settings for Microsoft Word and the widely used Times New Roman font.

While Glennon continues to insist that the documents could theoretically have been printed on a Vietnam War-era IBM Selectric, no one has been able to demonstrate this. Leading font developers say the technology simply did not exist 30 years ago.

One telltale sign in the CBS documents is the overlapping character combinations, such as "fr" or "fe," said Joseph M. Newcomer, an adjunct professor with Carnegie Mellon University. Blown-up portions of the CBS documents show that the top of the "f" overlaps the beginning of the next letter, a feat that was not possible even on the most sophisticated typewriters available in 1972. Newcomer calls the documents "a modern forgery."

Tests run by Thomas Phinney, fonts program manager for Adobe Systems, show that none of the possible font widths available on any typewriter or any IBM device from 1972 are able to produce an exact replica of the CBS documents. "Can they do something 'similar'? Sure," Phinney said. "Could they produce those exact memos? Impossible."

The Secretary Speaks

As conservative critics called for Rather's scalp, the spotlight turned to who provided the documents to CBS and whether that person was part of a hoax, or even a political setup.

CBS sources confirmed a report in Newsweek that one of the people Mapes interviewed was Bill Burkett, a retired Guard officer who has accused Bush aides of conspiring with the head of the Texas Guard to "sanitize" the president's military records. Burkett's accusations, which have been denied by the White House and Guard officials, have never been proved.

Since leaving the Guard, Burkett has run a ranch near Abilene, Tex., and been active in local Democratic politics, posting messages on the Internet urging other Democrats to wage "war" against Republican "dirty tricks." He has told reporters that he suffered from depression and had a nervous breakdown after the military declined to treat him for a tropical disease he contracted while on assignment in Panama.

CBS executives declined to address news accounts that pinpoint Burkett as the confidential source for the documents but say they weighed the fact that anyone turning over the material would not be a fan of the president. Burkett would not comment on whether he supplied the documents but said by e-mail to The Post that he would "encourage everyone to not cast too many doubts prematurely" on the "60 Minutes" broadcast.

Strong, the former Guard officer, said last week that when Rather showed him the documents, they contained a header showing they had been faxed to the network from a Kinko's copy shop in Abilene.

As the storm of criticism grew louder, Rather, Heyward and the program's staff still believed that the documents were genuine. They had no way of knowing that an 86-year-old woman in southwest Houston was discussing the controversy with a neighbor.

"I know Dan Rather is right," Marian Carr Knox, a former secretary in Bush's Guard unit, recalled saying. The neighbor said she should do something about it. So she called a Houston newspaper, Knox told CBS, but did not get a call back. Dallas Morning News reporter Pete Slover soon tracked down Knox and showed her copies of the Killian memos.

"These are not real," declared Knox, who said she handled Killian's memos. "They're not what I typed, and I would have typed them for him."

When a "60 Minutes" staffer showed Howard an online version of the Morning News story Tuesday night, "my initial reaction was not, 'Oh, my God, we're wrong,' " he said. But he immediately recognized that his program had to take her account seriously.

CBS got hold of Knox and had her on a plane to New York on Wednesday. Rather started the hour-long interview at 4 p.m., and while Knox said the underlying story was true -- that Killian had made such comments about Lt. Bush -- she insisted the memos were fake. Mapes had three hours to edit the interview for that night's "60 Minutes."

As they continue their investigation into whether they were hoaxed, CBS officials have begun shifting their public focus from the memos themselves to their underlying allegations about the president. Rather said that if the memos were indeed faked, "I'd like to break that story." But whatever the verdict on the memos, he said, critics "can't deny the story."

As the days begin to blur for Josh Howard, he embraces the same logic: "So much of this debate has focused on the documents, and no one has really challenged the story. It's been frustrating to us to see all this reduced to a debate over little 'th's."

Researchers Alice Crites and Meg Smith contributed to this report.

Producer Mary Mapes told her boss that she had the documents in hand the day after the GOP national convention ended. The report aired five days later.Dan Rather, a CBS mainstay, defended the network's report on the evening news, saying "some of these questions come from people who are not active political partisans" and that CBS "believes the documents are authentic."The dispute over memos of President Bush's National Guard record centers on the technology available in the early '70s, when the documents would have been typed.Former Texas lieutenant governor Ben Barnes told "60 Minutes" that he pulled strings to get Bush into the Texas Guard in 1968. Mapes had long called for Barnes, who has known Rather for three decades, to go on the record.