Journalists are paid to be skeptical and to distinguish facts from assertions: Don’t get too close to your sources and check what they tell you.

Rolling Stone magazine, it appears, ignored both principles in its explosive story, “A Rape on Campus.”

The 9,000-word article about Jackie, a University of Virginia freshman who alleged a frat-house gang rape, was apparently fraught from the beginning with gaps in basic reporting. The story’s writer, Sabrina Rubin Erdely, as well as a phalanx of editors, fact-checkers and lawyers who massaged the piece before publication, accepted Jackie’s account without locking down key details that would have confirmed, or at least plausibly substantiated, her harrowing tale.

Instead, Erdely’s story, published Nov. 19 to a thunderous and mostly positive reaction, appears to have been fatally defective. Major details, including the name of the fraternity in question, are in dispute or have been exposed as false. Jackie’s allies have distanced themselves from her and from Rolling Stone’s story.

And so, too, has Rolling Stone. The magazine backed away from the story Friday and placed the onus for its defects on Jackie. “In the face of new information, there now appear to be discrepancies in Jackie’s account, and we have come to the conclusion that our trust in her was misplaced,” wrote managing editor Will Dana in “A Note to Our Readers” posted on the magazine’s Web site. (The magazine did not return calls for further comment.)

He also wrote, ”Because of the sensitive nature of Jackie’s story, we decided to honor her request not to contact the man she claimed orchestrated the attack on her nor any of the men she claimed participated in the attack for fear of retaliation against her.”

Which, like the story itself, is not entirely accurate.

In interviews with The Washington Post and Slate, Erdely never asserted that she had agreed not to speak to the men in question — only that she wouldn’t name them in her story or talk about them afterward. Jackie “asked me not to name the individuals because she’s so fearful of them,” she told The Post. “That was something we agreed to. She was nervous to name the fraternity, too. I told her, ‘If we’re trying to shine light on this, we have to name the fraternity.’ ”

In fact, Erdely and her editor, Sean Woods, later acknowledged that the magazine had tried to find the men but failed to do so. “We did not talk to them,” Woods said. “We could not reach them.”

That should have been a red flag. In essence, neither writer nor editor could warrant that the men alleged to have committed a terrible crime actually existed.

That’s not to say that Rolling Stone should have abandoned the story altogether. But it does suggest the need for more reporting before going to press. The failure to ascertain the whereabouts of key actors in such a revolting drama left Rolling Stone not with she said/he said ambiguity — a feature of every alleged crime or scandal — but with half a story, told from a single viewpoint. Except for two vague, inconclusive quasi-denials by the president of the local Phi Kappa Psi chapter and the executive director of the fraternity, no aspect of Jackie’s story was rebutted.

Indeed, wrote Dana, “In the months Erdely spent reporting the story, Jackie neither said nor did anything that made Erdely, or Rolling Stone’s editors and fact-checkers, question Jackie’s credibility. Her friends and rape activists on campus strongly supported Jackie’s account.” But “friends” and “activists” have little incentive to be skeptical; that’s the reporter’s job.

To be sure, Rolling Stone was under no obligation to prove that Jackie’s account was true. That is a standard that eludes even the most rigorous trials, with eyewitness testimony and expert witnesses. News organizations, however, are responsible for independently verifying details, ascertaining facts, rooting out discrepancies and determining whether the discrepancies it finds are substantial enough to discredit a story.

How, for example, could Jackie recognize some of the men she said assaulted her in a room Erdely described as “pitch black”? How could she have exited the fraternity house via an entrance that, upon inspection, would have been shown not to exist? Did a party really take place at the fraternity on Sept. 28, 2012? (The fraternity maintains it did not.) If so, what did some of the partygoers, if not the alleged rapists, remember about that night? No such recollections were cited, leaving readers to wonder whether anyone was asked in the first place.

Erdely also adopted the “voice” of her protagonist as she described the alleged events. The style is common in magazine writing; newspapers are wary of it, lest it give too much credence to one perspective rather than multiple viewpoints. “You can have voice if the underlying facts check out,” said Emily Bell, professor of professional practice at Columbia University’s School of Journalism. “But you have to have the facts. [This] was a factual failing, not a presentational one.Voice is a secondary issue.”

Erdely herself deflected questions about her reporting by engaging in a bit of misdirection. When asked repeatedly by The Post last week about her contacts with “Drew” — the purported ringleader of the gang rape — she demurred, citing her non-disclosure agreement with Jackie. Her answer left the impression that she had indeed had such contact with Drew, but was bound not to talk about it.

The magazine could also have disclosed to its readers what it did not know and what its reporting could not show. The story didn’t disclose, for example, that Erdely couldn’t find Drew, nor a second fraternity member who Jackie identified.

Such caveats may weaken the overall narrative, but they help readers understand how strong the narrative is in the first place.

There’s another basic principle in journalism: Every story has two sides. In fact, every story has many sides. Rolling Stone decided to run with just one of them. To its everlasting regret.