STATE COLLEGE, Pa. -- Over four decades, the unsolved killing of a young graduate student in Penn State's vast Pattee Library has taken on a ghost-story mystique.
"It sounds like an urban legend," said Centre County District Attorney Michael Madeira. "Except it's real."
Amateur sleuths obsess over the "murder in the stacks." Newspapers revisit it on anniversaries and a subculture of poltergeist hunters regularly stokes the mythology online.
Even today, many Penn State students have heard about Betsy Aardsma, 22, of Michigan, who on the day after Thanksgiving 1969 was found among the musty library stacks, stabbed once through the heart.
Police interviewed 5,000 people but never made an arrest or named a suspect. Then as now, speculation filled the vacuum.
Was it Ted Bundy? A Vietnam veteran? A jilted admirer? A professor from her home state who later died in a car crash?
"You even hear the Zodiac Killer did it," said state Trooper Leigh Barrows, of the Rockview barracks, who has been investigating this cold case since February.
Betsy's story continues to resonate with each retelling -- especially for those who were on campus during those years. The Internet has fueled new interest about the killing in recent years, with Web postings presenting it as a titillating tale of the paranormal.
But for Trooper Barrows, 41, the slaying of this wholesome young woman will not be consigned to the realm of entertainment. At one time, 40 state troopers worked on the case. Now she's the only one, and she says she won't give up.
Working with the FBI, she's focused on a former student now in his 60s, seen often on campus at the time. She said she can't discuss more details.
"This is somebody I feel we need to talk to," she said in her office, where binders containing the 1,782-page case file cover an entire shelf. "I'm concentrating on an individual."
She's quick to offer a cautionary note: "I could be wrong." If she is, she said she'll keep looking. For inspiration, she keeps a photo of Betsy on her desk, near a snapshot of her own 21-year-old daughter.
She's not alone in her devotion.
"We all think it's a fascinating case," said Ron Tyger, 70, a former state police investigator who still talks to his old colleagues about the murder. "Not a day goes by that you don't think about it."
Sascha Skucek feels the same way, even though he's only 33. A lecturer in English at Penn State, he's spent years researching and writing about the case extensively for State College Magazine. He carries a photo of Betsy in his wallet and has visited her grave in Michigan.
"I think this case grabs hold of you," he said. "It's become more than a story to me. I want to solve it."
Other amateurs have also explored the case. A retired Wall Street consultant, a 1969 Penn State grad, started writing a book about it but never finished. An investigator for the A&E network's "Paranormal State," a 2006 graduate, filmed a segment on it, and an author wrote a 1990 science-fiction novel based on it.
And there's Derek Sherwood, 30, a furnace salesman in York whose former Web site, whokilledbetsy.com, kept tabs on the investigation. His dad once worked at Penn State and his sister graduated from the school, where she was terrified to venture into the stacks.
Like Mr. Skucek, Mr. Sherwood says Betsy's case deserves to be treated with dignity out of respect for her and her family in Michigan.
"I just thought that it was bad that her whole life had been reduced to this ghost story and I thought, at the very least, it would be nice to bump it up and put some facts out there so that people could see, 'Yeah, this really did happen,' " he said in one online interview.
Trooper Barrows said that while some writers, especially Mr. Skucek, have proved helpful and dedicated, others have spread misinformation.
"It can be tough to separate fact from fiction," she said.
Betsy's family has talked about the case over the years, but now say they've had enough of the media.
"I'm not giving any more interviews," said Carole Aardsma, Betsy's sister.
The killing stunned everyone on the bucolic campus nicknamed Happy Valley, especially since Betsy had no enemies. A native of Holland, Mich., and a graduate of the University of Michigan, she was smart and good-natured.
"What I've said before in interviews is that she was squeaky clean," Mr. Tyger said. "There was no motive. If there had been a motive, it would have been solved 40 years ago. You go crazy trying to figure out why this happened to her."
Betsy chose Penn State for her graduate work to be near her boyfriend, David Wright, a medical student in Hershey and now a doctor in Illinois.
It was a good time to leave Michigan. From 1967 to 1969, seven young female students were murdered around Ann Arbor. Serial killer John Norman Collins, later dubbed the Co-Ed Killer, was convicted of one of them in 1970 and is suspected in the others.
"That's just one of many strange aspects of this case," said Trooper Barrows.
Police in Pennsylvania and Michigan later looked at Mr. Collins as a possible suspect in Betsy's killing, but ruled him out.
Betsy spent Thanksgiving 1969 with her boyfriend, where he lived with several other medical students, and took a bus back to State College on Thanksgiving night to get a jump on a paper the next day.
Mr. Wright stayed in Hershey, where he took part in a study group the next day. Police interrogated him repeatedly after the killing, but his friends said he never left. In addition, he and Betsy had a good relationship; she wrote him a letter almost every day.
At about 4 p.m. on Friday, Betsy left her dorm room on campus with her roommate and walked to the library. She stopped to see an English professor, whose office was in the basement, and then headed to the core, a multistory central area containing shelf after shelf of books.
Everyone on campus calls it the "stacks." In 1969, it was a creepy place, with low ceilings, dim light and narrow staircases.
Stories vary about what happened next. But between 4:30 and 4:45 p.m., Betsy collapsed among the stacks. Some people reported hearing a scream, but some said they heard only falling books or shelves.
Students found Betsy on the floor and initially thought she had fainted. As she collapsed, she clutched at books on a shelf, which fell on her.
No one noticed blood initially because she was wearing a red jumper-style dress. Paramedics took her to the campus health center, where a doctor discovered a knife wound. Autopsy photos show massive bruising around the entry point, indicating that someone struck her hard with a single downward thrust that penetrated her heart.
She bled into her lungs, which is why there wasn't much blood at the scene, and was pronounced dead a half-hour later.
In the library, no one knew she'd been killed. She had urinated after being stabbed, and a custodian who cleaned the area inadvertently compromised the crime scene.
Police still have that dress and other evidence from which they might be able to obtain a DNA sample -- if the killer left behind a hair or blood. The evidence has been submitted to the state crime lab but the results aren't back.
Early in the investigation, 40 troopers staffed a temporary headquarters on campus. From the start, there were conflicting witness reports about suspicious men in the library.
George Keibler, 78, the former state police sergeant in charge of the case, said one witness saw a blond man running from the stacks who said, "Somebody better help that girl." He was never found. Troopers also never recovered a weapon.
They conducted thousands of interviews, sometimes using polygraph tests and even hypnosis, and released three composite sketches of witnesses they couldn't find. But the drawings were so generic that they could have depicted almost anybody.
An early suspect was Robert Durgy, 27, an English professor who died in a car crash near Lansing, Mich., about three weeks after Betsy's killing. He, too, had come to Penn State from the University of Michigan in the fall of 1969.
He had also been a teaching assistant in English at Michigan when she was there. Troopers investigated and cleared him.
Serial killer Ted Bundy surfaced as a possible suspect because he had attended Temple University in 1969 and spent time in university libraries.
Some investigators suspected a former military man because of the nature of the wound. Most knife attacks involve multiple stab wounds, but this one was almost surgical in its precision -- the way a trained Vietnam veteran might kill.
Troopers also zeroed in on rampant sexual activity known to take place in the library.
"The whole ... library was a den of perverts," said Mr. Keibler.
In one secluded area near the murder scene, Mr. Tyger said police found a chair, a half-empty can of root beer and porn magazines tucked among the books. A black-light examination also turned up semen residue on the floors and on the books that had been there for years.
Those discoveries led to another theory: That Betsy might have interrupted some illicit sexual activity and was killed to keep her quiet.
But one problem with narrowing down suspects, Mr. Keibler said, is that all kinds of weird characters hung out in the library. Although some media accounts have portrayed the building as nearly deserted, Mr. Keibler said a counter at the front entrance recorded 3,219 people who came and went that day.
"There were lots of people there who were screwed-up," he said. "You had people on LSD, you had people going there for sex. There are as many theories as you can ever imagine."
But Trooper Barrows thinks Betsy and other young women had seen the suspect before on campus. There were no defensive wounds, as are typical in knife attacks.
"There was no struggle, she didn't run," she said. "I think that she knew who her killer was. I think that she was familiar with him, that she recognized him, and that she was not afraid of him."
After the initial flurry of activity in 1969, the investigation petered out, although over the years a few intriguing developments have cropped up.
On Nov. 28, 1994, the 25th anniversary of the murder, a library worker found a candle burning in the aisle where Betsy was killed. On the floor was a message scrawled in red marker: "R.I.P. Betsy Aardsma, born July 11, 1947, died November 28, 1969. I'm back."
Near the message, the worker also found original copies of news stories about the case, although some of those would have been available in the library. Another shrine appeared in 1999, but not in the same place. Police suspect both incidents were pranks.
Then there was the postcard mailed from Atlanta to campus police in the 1970s that said, "You never did catch the guy who killed that [expletive] in the library."
That also led nowhere; anyone could have sent it, and lots of Penn State grads live in the Atlanta area.
As with any 40-year-old case, many of the witnesses now are dead or scattered across the country. But Trooper Barrows said she is methodically tracking down every name in the file.
"If they're still alive," she said, "they're going to get a call from me."
Torsten Ove can be reached at firstname.lastname@example.org or 412-263-1510.