Serial killer Timothy Krajcir was an apt student of law enforcement.

At the age of 30, freshly released from prison on rape charges, Krajcir enrolled in college in the late 1970s to study psychology and the criminal justice system. At the same time, authorities said, Krajcir murdered six women in two states, hiding his crimes from dozens of investigators by using the tactics he learned in school.

Authorities say Krajcir is a rare specimen -- smart enough to elude police during his crime spree and apparently private enough to keep his deeds secret afterward. He eventually graduated from Southern Illinois University in Carbondale, Ill., with a degree in law enforcement.

"If he was studying criminal justice and law enforcement, he definitely would know what police were looking for and how to avoid detection," said James Smith, a Cape Girardeau police detective who helped link Krajcir to five homicides dating back 30 years.

He also has an IQ of 120, police said.

Krajcir admitted this month to nine homicides in all, according to Cape Girardeau County Prosecuting Attorney Morley Swingle.

Krajcir was charged Monday with five counts of murder and three counts of rape in Cape Girardeau after pleading guilty the same day in Illinois to the 1982 murder of fellow SIU student Deborah Sheppard.

Prosecutors are building cases in the other three homicides, which Krajcir has admitted to in states outside Missouri and Illinois, Swingle said.

Police have released no details about those cases.

Public defender Patricia Gross represented Krajcir in Sheppard's killing but would not comment Tuesday, according to her assistant. Krajcir doesn't have an attorney in Missouri, according to court filings.

For decades, Krajcir sat in Illinois prison on a rape charge, telling no one about the murders while detectives in different states struggled to close the cases, Smith said.

Waited in parking lots

It appears one of the most important strategic decisions Krajcir made was to murder women in a city where he did not live. While Krajcir attended class 45 miles northwest of town, detectives in Cape Girardeau focused on local suspects, said former detective M.C. Hughs.

"Our thinking was that [the killer] set back and they watched these women and got down kind of a routine," Hughs recalled.

In fact, Krajcir drove to Cape Girardeau and waited in shopping center parking lots, stalking women until he found one he liked and then followed her home, said Carbondale Police Lt. Paul Echols, who has interviewed Krajcir several times.

Krajcir had no connection with the city beyond using it as a hunting ground, Echols said.

He was a licensed EMT and drove an ambulance that made stops at area hospitals, said police chief Carl Kinnison.

Cape Girardeau police found Krajcir's first victims Aug. 15, 1977. Mary Parsh, 58, and her daughter, Brenda, 27, were found in their home, nude, lying side by side on the bed, their hands tied behind their backs. Each was killed by a gunshot wound to the head.

Next came Sheila Cole, who was kidnapped from a Wal-Mart parking lot and killed in November 1977. Her body was found at a rest stop in Southern Illinois.

In 1982, two homicides in Cape Girardeau were strikingly similar to the killings of Mary and Brenda Parsh. In both cases, a man broke in through a bathroom window and waited for his victim to arrive home.

In January 1982, Margie Call, 57, was found dead in her home, lying on her bed partially nude. Her hands were crossed behind her back and it appeared they had been bound. She had been raped and strangled.

In June 1982, 65-year-old Mildred Wallace was found killed and partially nude in her bed. Her hands were tied behind her back and she had been shot in the head.

Hughs said similarities in most of the murders, like the tied hands and the killer waiting at home, led investigators to believe the killings were connected. But it was tough to conceive the killer might be a stranger who chose victims at random.

There was a lull in Krajcir's murder spree when he was jailed in Illinois in 1979 for having sex with his Carbondale landlord's 13-year-old daughter. A judge conditionally released Krajcir in 1981, and he reportedly returned to Pennsylvania to be with family.

In 1982, Krajcir was arrested on sexual assault charges and served time in a Pennsylvania prison. The crime violated his parole in the Illinois case, so when the Pennsylvania term expired in 1988, he was brought back to Illinois to resume serving the sentence. He has been in the state's custody since.

He has had the option of attending programs that would have helped him work toward release, but has chosen to remain in prison because he knows he is a threat to the community, Kinnison said.

Echols said advances in DNA technology eventually let him test a small sample from Sheppard's killing. It matched Krajcir's, which was in a database. Smith then did a similar test with material from Wallace's killing, which matched Krajcir.

After initially denying his involvement in the murders, Krajcir confessed Dec. 3, Smith said.

It's unclear how much Krajcir learned about police investigations before graduating from SIU with a degree in administration of justice and a minor in psychology.

But part of his interest might have stemmed from the burning question that so many people have now.

"He said initially he was trying to figure himself out," Smith said. "But he failed, obviously."

Staff writer Bridget DiCosmo contributed to this report.