At 2:04:22 a.m., as the night of May 6, 1998 slipped into the day of May 7, Parmatma Greeley called 911.

Greeley: "Hello. My next door neighbor, I just heard her yelling for help." Operator: "And what's wrong?" Greeley: "We're on the second floor. I'm on, we're on one side and she's on the other. And I just heard. her yell help. I knocked on the door and I just heard like a. like a choking-type sound and I just called." Operator: "We'll have someone out as soon as possible."

There was no way that Greeley could have known that at that moment, Troy Graves, the so-called "Center City Rapist," was choking Shannon Schieber to death.

The process by which a forensic pathologist determines a time of death is notoriously inaccurate. Stomach contents, potassium level in eye fluid, rigor mortis, lividity, body temperature; all these factors are used. But these indicia vary from person to person, and so accurately determining a time of death closer than within a few hours is difficult, if not impossible. In a case like the murder of Shannon Schieber, where a few seconds might have been the difference between life and death, pinpoint accuracy can be vitally important.

13 hours.

That's how long it took to discover Shannon Schieber's body. An autopsy was not performed for an additional 18 hours. That makes determination of an exact time of death even more difficult, but court documents filed in the Schieber family's case against Officers Steven Woods and Raymond Scherff, the two policemen who responded to Parmatma Greeley's 911 call, provide some insight as to when Schieber's final moments may have come.

Strangulation, despite what movies often depict, is not a quick process. Mercifully, thankfully, the time it takes for a strangulation victim to lose consciousness is short. But just how short that time is can be a source of confusion. Forensic pathologists are trained in their craft through a mentoring process, and depending on that mentor, one pathologist may have an entirely different view of a situation than another. Dr. Vincent DiMaio, the Chief Medical Examiner for Bexar County in San Antonio, Texas, is an expert witness for the city of Philadelphia. He believes that it takes only five to ten seconds for a strangulation victim to lose consciousness, and another five minutes for brain death. He has testified that "once you get to seven or eight minutes, you're just not coming back." Assuming that Troy Graves began to strangle Schieber at about 2:02 a.m., two minutes before Greeley's 911 call, Schieber would have been brain dead by 2:10 a.m.

When the Schieber family -- Shannon's mother Vicki, father Sylvester and brother Sean -- filed suit against Woods and Scherff, it hired Dr. Michael Baden, a distinguished forensic pathologist who served on the congressional committees that investigated the deaths of John F. Kennedy Jr. and Martin Luther King Jr., as an expert witness. His estimate of the length of the strangulation process is much longer than DiMaio's. Instead of five to ten seconds, Baden says that the time for the loss of consciousness is closer to three minutes. Again, assuming that Graves began to choke Schieber at about 2:02 a.m., Schieber would not have been unconscious until 2:05 a.m. Brain death, Baden says, would have taken another five to eight minutes, and then it would have been another five to ten minutes before her heart stopped beating. Shannon Schieber could still have been alive as late as 2:23 a.m.

In the newspaper reports that followed Shannon Schieber's death, a few words come up often. Words like "brilliant," "achiever" and "outgoing." She was 23 years old. She had graduated from Duke University with three majors -- philosophy, mathematics and economics. She had just finished her first year as a doctoral student at Wharton, and though according to The Philadelphia Inquirer she found it to be "socially isolating," she managed to get out into the city to tutor and to help administer an economics program at West Philadelphia Catholic High School.

Shannon Schieber was beautiful, too. Tall, and thin. 5'10", 135 pounds. About the same size as Troy Graves. Her height might have been fatal for her.

Frederick Kingston is an FBI profiler. In 1999, he compiled a report on the then-unknown attacker of Shannon Schieber, who had by then been linked to five other rapes. Although the report is restricted to the public -- a confidentiality agreement signed by both parties in the civil trial restricts much of the evidence -- snippets are available: the Inquirer obtained part of the report in 2000 when the Schieber family's legal team submitted it into evidence.

Kingston paints a portrait of a troubled man who had no real desire to harm any of his victims. He saw his assaults as "dates," sometimes trying to engage his victims in pillow talk after he assaulted them. He told one woman that she could prevent attacks from other men by putting bars on her window.

But Schieber was the first to seriously physically threaten him. In his report, Kingston says that she was "brilliant... extremely athletic; she is one who, I think, is a very no-nonsense, take-charge kind of driven person. Her demeanor is such that she would be more likely to aggressively resist his attempts to rape her." This, he believes, combined with Greeley's knock and the police search of the premises, must have spooked Troy Graves. "It was not the offender's [initial] intent to murder Shannon Schieber," Kingston's report says. "It was the victim's aggressive resistance and the offender's fear that caused him to murder. He knew that, with police officers at the door, if she screamed again, it would surely result in his immediate arrest."

Greeley first believed something was wrong in his neighbor's apartment at about 1 a.m. when, according to a deposition, he heard "a scuffle" next door. Amy Reed, a graduate student at Penn, later said that at around that time she heard something fall to the floor in Schieber's apartment, which was above hers, but didn't think anything of it. Greeley, however, did. He and his girlfriend, Leah Basickes, who was also a graduate student at Penn, listened for more sounds. When they subsided, Basickes went to bed, but Greeley stayed awake, listening. It was at about 2 a.m. that he heard, or thought he heard, Schieber's scream. From there, it all moved quickly.

2:04:22 a.m., Greeley calls 911.

2:05:10 a.m., the radio puts out the "Priority 1" call -- the highest priority 911 call a civilian can make.

2:11:48 a.m., Officer Woods and Officer Scherff arrive in separate cars.

2:16:57 a.m., Scherff, leaving Schieber's apartment building at 251 S. 23rd St., calls it in: "Yeah, that's gonna be unfounded" -- police code meaning that no crime has been committed.

Of course, it's not all quite that simple. As Greeley waited the seven minutes it took Woods and Scherff to arrive, he began to panic. He went downstairs looking for Reed's boyfriend, thinking that together they could break down Schieber's door, but Reed's boyfriend was not in. It was there that Woods and Scherff found Reed and Greeley. The four of them walked up to Schieber's apartment door and knocked but received no response. Christine Ritter, who lived on the third floor above Schieber, came downstairs, awoken by the police officers' knocks. Woods and Scherff interviewed the three residents: Reed and Ritter had heard nothing, while Greeley maintained that he had heard a scream and a choking sound coming from Schieber's apartment. But as the officers continued to question him, and discussed the possibility of breaking down Schieber's door, he began to feel certain. Greeley's deposition in the civil suit shows this.

With little certainty in their minds coming from Greeley, Woods and Scherff searched the area around Schieber's apartment, looking for signs that entry had been forced through the front door, the window or the door to her apartment's balcony. There was none.

For a second time, now with the heel of their nightsticks, Woods and Scherff knocked on the door to Schieber's apartment and identified themselves as police. No one responded.

The landlord didn't live in the building, and no one else had a key to Schieber's apartment. Woods, Scherff, Greeley, Reed and Ritter began to discuss the possibility that the door to Schieber's apartment should be broken down. Here, the court record becomes hazy, but everyone agrees that at some point, Greeley said he would be embarrassed if the door were broken down and nothing was happening. In his deposition, Greeley explained it this way: "I thought they were going to break down the door, and I hadn't heard any sounds in so long that I was sort of just at this point... [waking] up a bunch of people and I was just... let me phrase this properly. It was my ego on the line. I thought he was going to break down my neighbor's door on my call, so it would be embarrassing if you break down your neighbor's door and there's nothing happening."

With no signs of forced entry, and a witness who was, in their minds, uncertain as to what he had heard, Woods and Scherff left 251 S. 23rd St -- after telling Schieber's neighbors to call 911 if they heard anything else. None of the five could be reached for comment. Basickes, Greeley's girlfriend at the time, declined to comment.

The next day, Sean Schieber was in Philadelphia, and he was supposed to meet his sister for lunch. When he went to meet her at work she wasn't there, and her co-workers seemed concerned. Schieber went to his sister's apartment and found the sliding glass door to her balcony open. He knocked on Greeley's door, and together the two forced their way into Shannon Schieber's apartment. They found her naked, lying face-down on the floor. Greeley later said, in a November 29, 2000 article in the Philadelphia Daily News, that Sean Schieber "dropped in the fetal position on the floor crying." And for the last time, Greeley called 911 for Shannon Schieber.

On October 26, 1998, about five and a half months after the murder, Sylvester, Vicki and Sean Schieber filed a federal civil rights lawsuit against Officer Woods, Officer Scherff and the city of Philadelphia. At a press conference held that day, Sylvester Schieber said that "our requests for a formal investigation of the 911 incident have been met with silence and total rejection. These rejections have left us no real alternative but to file a lawsuit." The Philadelphia Police Department stood by their officers, and then-Police Commissioner John Timoney continued to reiterate that every effort was being made to bring Schieber's killer to justice.

Now, five and a half years later, the Schiebers are hoping for a conclusion to the saga. A pre-trial hearing is scheduled for January 30th. Jury selection will most likely take place on February 10th or 11th. But the lawsuit has changed somewhat. Woods and Scherff are no longer defendants -- in February of 2003, the U.S. Court of Appeals for the Third Circuit reversed District Court Judge Norma L. Shapiro's rulings and granted summary judgment for the two officers, dismissing the case against them before it could ever go to a jury. There are very definite rules about when a party, acting on behalf of the state, can be held liable for its actions, and those actions cannot just be negligent. They must be enough to "shock the conscience." By a 2-1 vote, the Court of Appeals ruled that Officer Woods and Officer Scherff had done nothing that would rise to that standard.

So now, the Schieber family and their lawyer, Penn Law Professor David Rudovsky, are trying a new angle. A 1999 investigation by the Inquirer revealed that the Philadelphia Police Department had been for years downgrading and not investigating reported rapes. The sex-crimes unit "put about 30 percent of its caseload in a statistical limbo between 1984 and late 1997. The complaints were placed in Code 2701, 'investigation of person,' so they would not appear in the city's crime statistics," reported Inquirer staff writers Mark Fazlollah, Michael Matza, Craig R. McCoy and Clea Benson on October 22nd, 1999. The Schieber family alleges that this practice discriminated against women and that it kept knowledge of a serial rapist from Woods and Scherff and may have affected their actions on the night of Schieber's murder. The city, however, says that Woods and Scherff did know about the previous rapes in the Rittenhouse Square area.

"Hindsight is 20-20 vision," says Jeffrey Ian Ross, a criminologist and professor at the University of Baltimore. "In retrospect, I'm sure those officers are saying, 'I wish we would have kicked down that door.' I'm sure the police officers feel bad about it, but I think the police officers are in the clear and the city is in the clear.

"But in terms of the downgrading of sex crimes, there may be some wiggle room on the part of the plaintiff's lawyer."

Shannon Schieber may have died on May 7, 1998, but her memory lives on. Her story was featured on America's Most Wanted. Her name lives on, too; the Shannon Schieber Retirement Policy Institute works to keep policy-makers informed about the issues surrounding retirement, and in Washington, DC, near her hometown of Chevy Chase, MD, there is a roofing fund in her name, helping to repair roofs for people who could otherwise not afford to. "We hope that Shannon's spirit lives on," Sylvester Schieber said the day his family announced their lawsuit, "in the lives of the people of Philadelphia who will benefit from a better trained, more responsive and more effective police force"