For nine years, Chris Cosgriff has meticulously collected details, photographs and badge numbers of law enforcement officers slain in the line of duty around the country and has displayed the information in online tributes. He labors, he says, so that officers such as Prince George's Cpl. Steven Gaughan, and their sacrifice, will not be forgotten.

Gaughan, 41, was shot June 21 during a confrontation after a traffic stop at an apartment complex in the Laurel area. Robert M. Billett, 43, of Bladensburg was charged with first-degree murder and other offenses. He is being held without bail.

Unlike Gaughan's highly publicized death, the slaying of Arlington County Special Officer Louis F. Shaw nearly 70 years ago went largely unnoticed until Cosgriff's work. Shaw was publicly recognized for the first time in May during National Police Week, an annual gathering in Washington attended by thousands of officers from around the world to honor those killed while on duty.

Cosgriff's research into Shaw's death also led to the officer being honored by the Arlington County Police Department, which had known nothing about the incident because the agency wasn't formed until several years after he was killed. An official record of the death was not kept by the county; Cosgriff learned about it while researching another police killing in the archives of The Washington Post.

Relatives of Shaw knew most of the details of his death but hadn't thought to request that his name be added to the blue marble walls of the National Law Enforcement Memorial, which sits on Judiciary Square in the District and bears the names of more than 17,000 fallen officers.

Frank Marcey, 67, Shaw's nephew, had an idea while growing up of what had happened to his uncle, but his relatives didn't talk much about it. When he was a child, mementos of his uncle's career were all around him: the police-issued handcuffs, badge and pistol. Marcey gave the pistol to Cosgriff, who said he plans to donate it to a soon-to-be-built law enforcement museum.

"Here it's been 70 years and most of my family is gone, but we're finally learning the real details," Marcey said in a phone interview from his home in Sterling. "It's been a very emotional, and pleasurable, time for us."

None of it would have been possible, Marcey said, had Cosgriff not dedicated himself to learning the truth about fallen officers.

"He did a tremendous job," Marcey said. "For him to do all he did, we're just very honored."

Cosgriff, 27, created his Web site, at www.odmp.org, while a freshman at James Madison University in Harrisonburg, Va. Working from his dorm room, he designed a basic site after being angered by an article in The Washington Post about a Prince George's County man who was released from prison 17 years after killing two county police officers. Around the same time, an officer from the Philadelphia Police Department was killed while trying to stop a bank robbery.

"I had learned a little about Web sites, and so I just created it," Cosgriff said. He wrote a few sentences about the Jan. 2, 1996, slaying of Philadelphia officer Lauretha Vaird. A few days later, a patrolman with the police department in Fort Lauderdale, Fla., was killed by gunfire. Cosgriff added the officer, Bryant H. Peney, to the site.

"His twin brother found the site and e-mailed me to thank me, and it meant a lot to me. It's what got me going to really honor all officers on the site, and over time it's just grown," said Cosgriff, a slender man with a boyish face and closely cropped hair.

During its first month, the Web site, called the Officer Down Memorial Page, had 240 visitors.

It now has about 16,000 different visitors a month who sift through the lives of 17,000 officers from all 50 states and U.S. territories. Six volunteer researchers, including Cosgriff, work on the site, investigating all claims of long-forgotten line-of-duty deaths. They are now researching about 300.

Cosgriff spends about 30 hours a week working on and adding to the site, he said, mostly from a computer in the basement of his home in Oakton. That's in addition to his full-time job as a solutions engineer for the technology firm NovusCG, based at the Pentagon.

Last year, Cosgriff and his volunteers discovered 49 forgotten deaths in addition to Shaw's, including those of two Loudoun County police officers whose departments did not know of their on-duty deaths.

For example, in Middleburg, Sgt. Henry Seaton, whose rank was the equivalent of today's police chief, was stabbed to death in 1899 by a man he had arrested for being drunk and disorderly.

In honor of Shaw and Arlington County's five other line-of-duty deaths, a bronze statue of a police officer was erected in the courtyard of the county's police headquarters during Police Week. Below the statue is a description of Shaw's death on Dec. 6, 1935.

Shaw, 28, had no chance of survival when the police car in which he was riding was struck by a Shell Oil Co. truck about 5 a.m. The cruiser was thrown 75 feet into a telephone pole, rupturing its gas tank and engulfing it in flames. Shaw and a prisoner he and his partner were transporting to the county jail died instantly in the fire. His partner had stepped out of the vehicle to survey an hours-old accident scene caused by the prisoner when the crash occurred.

Thirty years earlier, a Fairfax County sheriff's deputy was slain while trying to arrest a man. But while growing up in Northern Virginia, Anita Malcolm Smith knew only two things about her great-uncle George A. Malcolm: In the early 1900s, he served as the head instructor of a Lorton school. And he was murdered, not far from the campus.

Smith, 56, had seen a photo of the young Malcolm, a slender, handsome man with thin, casually pursed lips and soft eyes looking away from the camera. Her family didn't talk much about his slaying, she said, and those who were alive when he was killed in 1905 were no longer living when she was born.

"All we knew was that he was shot while trying to defend a student," she said in a telephone interview from her home in the Tidewater area.

Cosgriff called Smith last year. He was doing research on other on-duty deaths when a brief article in The Post caught his attention. It described the gunfire that erupted near Lorton on April 6, 1905, during which a Fairfax County sheriff's deputy was struck five times while trying to arrest a man who had been harassing female students at the Lorton Valley school, where the officer also worked.

The young deputy was Malcolm.

"I was baffled," Smith said. "None of us had any idea he was a police officer."

Nor did the county's sheriff's office, which had no record of the killing.

In what is considered the ultimate tribute in law enforcement, Malcolm's name was engraved on a wall of the National Law Enforcement Memorial, more than 100 years after he was killed.

Malcolm and Shaw were among four Washington area officers whose line-of-duty deaths were recognized for the first time this year, some more than a century after they were buried, due in large part to the persistent efforts of Cosgriff, whose work has led to the discovery of more than 500 deaths.

What began as an experiment for an 18-year-old kid who dreamed of becoming a police officer has evolved into a research tool for academics and a teaching and training resource for hundreds of police departments across the country. Prince George's County is among the local jurisdictions that use the site to teach recruits about the perils of policing.

The site has also helped Cosgriff forge important relationships with those involved in the National Law Enforcement Memorial, he said. He credits the memorial with giving him a list of 10,000 officers killed before 1996 to add to his site. When he discovers a new death, he sends the information to memorial officials, he said.

It is a carefully orchestrated process, one that requires many hours a week. Cosgriff, who doesn't earn a penny from the site, and the other volunteers send copies of newspaper articles, death certificates, filled-out National Memorial nomination forms and stamped envelopes to police chiefs and sheriffs around the country. All they have to do is sign the forms and return them, but many don't, he said.

But even if the names don't make it onto the National Memorial, either because the agencies don't respond or the fallen officers don't make the cut for whatever reason, the dead are memorialized online, a source of comfort to their relatives, Cosgriff said.

After each summary of an officer's death is a link to a "reflections" page, a space in which visitors can leave comments. Most thank the officer for his or her courage and commitment, while other comments are much more personal.

"Thank you for everything you have been to me," Amy Elizabeth Gray wrote to her father, Ernest Gray, a Pennsylvania officer whose on-duty death in 1984 was finally recognized during Police Week this year because of Cosgriff's efforts. "Though I may not have had much time with you, you have been a huge inspiration in my life. I will never forget you. I love you."

Gray, an officer with the Pennsylvania Public Utility Commission who was 33 when he died in an accident on a rain-slicked road while on his way to a call, is the brother of Cosgriff's boss, Bob Gray, 47. Gray said last week that Cosgriff's determination to honor his brother was heart-warming.

"It meant so much to us that he would take that time," he said.

That's all the thanks that Cosgriff, who still harbors dreams of becoming a law enforcement officer someday, said he needs.

Cosgriff wanted to join the Fairfax County Police Department after high school but didn't meet its age requirement of 21. He didn't know what to do until he turned 21, so he decided to go to college, where he fell in love with computers and technology and learned to create Web sites.

"I'm not looking for recognition or money," he said. "I hear from widows and children and relatives about how much the site means to them. It makes it all worth it for me, and it keeps me going. I feel like I know these officers now."

Last month, Cosgriff met -- figuratively -- five more fallen officers, including Gaughan. Within hours of Gaughan's death, Cosgriff had summarized the slaying and uploaded a picture of the officer onto the site.

Clockwise from top left: Chris Cosgriff, who created the Officer Down Memorial Page, at a ceremony at the National Law Enforcement Memorial; Suzanne Galinski, standing next to Officer Adam Stone, at the memorial in Arlington that honors her husband, Officer Arthur Chorovich, who was killed in 1964; Cpl. Steven Gaughan of Prince George's County, who was killed while on duty last month; the funeral procession for Gaughan in Davidsonville; Cosgriff at the Arlington memorial; Alexandria Officer Tara Delio wiping away tears at the burial service for Metro Transit Officer Marlon F. Morales, who was fatally shot in 2001; and Fairfax County sheriff's deputy Paul R. Camarca making an etching of sheriff's deputy George A. Malcolm's name after it was added recently to the national memorial.Louis F. Shaw, an Arlington officer who was killed nearly 70 years ago, recently was memorialized with a plaque at the county's police headquarters. Fairfax County sheriff's deputy George A. Malcolm, at right, was killed in 1905. Both men were honored because of research done by Chris Cosgriff, who runs a Web site that lists officers killed in the line of duty.George A. Malcolm's name recently was added to the list of officers killed in the line of duty on the National Law Enforcement Memorial. Malcolm, a Fairfax County sheriff's deputy, was shot in 1905 while trying to make an arrest.