Despite a stunning drop in homicides in the District — from a peak of 482 in 1991 to 108 last year — murder remains a stubborn crime to solve and prosecute in the nation’s capital.

A Washington Post review of nearly 2,300 slayings in the city between 2000 and 2011 found that less than a third have led to a conviction for murder or manslaughter, although the numbers have improved in the past few years. More than 1,000 cases remain unsolved.

In a 15-month study, The Post individually tracked every homicide in the District between 2000 and 2011 to learn what ultimately happened to each ensuing case. Such studies, known as longitudinal, are not generally produced by law enforcement, because they are considered to be too time-consuming.

The study found that out of 2,294 homicides in the period, 30 percent have led to a conviction for murder or manslaughter, according to the analysis of police and court records. The Post last published a similar study in 1993, when it found that 25 percent of the 1,286 homicides between 1988 and 1990 led to such a conviction.

The latest study shows that from 2000 through 2006, under Police Chief Charles H. Ramsey, the number rose to 29 percent for the 1,544 homicides over that period.

This interactive map has details about 2,294 homicides that occurred between 2000 and 2011 in the District of Columbia. Find the killings in your neighborhood, follow the trends over time, and learn how the victims died and what happened to their cases.

The trend has continued to improve in recent years for the 750 homicides under Cathy L. Lanier — to 35 percent between 2007 and 2009 — and analysis indicates it will continue to rise in subsequent years as pending cases are adjudicated.

The study shows that even as homicide trends improve — as caseloads lessen and police pursue innovative crime strategies — a hard residue remains of killings that are difficult to solve and prosecute, mainly involving drugs or retaliation.

“This is a good-news, less-good-news story,” said Richard Rosenfeld, a criminology professor at the University of Missouri at St. Louis. “The good news is that there’s a drop in homicides in the District of Columbia and the United States. What does that mean? What D.C. and other cities are faced with is a different mix of cases that end in homicide, and those cases are tough to prosecute.”

U.S. Attorney Ronald C. Machen said the Post study is “not necessarily a reflection” of how well his office is prosecuting homicides.

“What you’re really measuring in my view is, okay, a person is killed on the street: What is the likelihood that person would get convicted at the end of the day? That’s different than conviction rate,” he said. “What you’re measuring, to me, is more a reflection of, is the community coming forward and giving you enough information to make an arrest? If you never have enough information to even arrest somebody, you can’t hold them accountable for those murders.”

He said that cooperation from the community has improved in recent years but that historically it has been a problem.

“It used to be, when I was in this office before, people would rather talk to anybody than a prosecutor or police officer,” said Machen, who worked as an assistant U.S. attorney in D.C. from 1997 to 2001, including a year in the homicide section. “We would have people whose family members have been killed and they would not talk to us about the murder.”

In recent years, the District of Columbia has experienced a historic drop in the number of homicides and a concurrent rise in the percentage of cases closed by police.

Machen said his office measures conviction rates based on the number of people indicted by a grand jury who ultimately plead or are found guilty. Last year, 70 people were convicted of murder or manslaughter and 21 others were acquitted or dismissed after indictments, resulting in a 75 percent conviction rate, he said. Two others pleaded guilty to lesser charges.

“Over the last few years, we’ve been doing pretty well,” said Machen, who took over the office in 2010.

Rosenfeld said killings today more often involve two criminals and are harder to close or prosecute, because witnesses might not be available or may be intimidated or reluctant to come forward. Decades ago, more homicides involved people who lived together, and such cases were easier to solve because there was usually no question about who did the crime, he said.

“Murders are now inherently more difficult to prosecute — starting with an arrest,” Rosenfeld said.

The Post’s findings support Rosenfeld’s view.

Of the 2,294 homicides since 2000, only 148 were classified in police records as domestic cases — 400 were classified as drug killings and 331 as retaliation slayings, which usually involved drugs or gangs. The Post found that 57 percent of domestic cases ended in a conviction for murder or manslaughter, compared with 22 percent for drug killings.

“So much depends on the kind of homicides,” said Richard Berk, a professor of statistics and criminology at the University of Pennsylvania.

Aside from convictions, The Post’s latest study also looked at what happened to homicide arrests over time. They also have been rising in recent years, hitting a high of 63 percent last year, the study showed. The overall arrest rate for homicides between 2000 and 2011 stood at 48 percent, compared with a 57 percent rate between 1988 and 1990, when the crack cocaine wars ravaged the city.

One reason that more arrests led to fewer convictions in the earlier years is that more cases were dismissed back then.

The statistics show that a lessening caseload in recent years has gone hand in hand with far fewer charges that end up being dismissed. Twenty years ago, 33 percent of all cases closed by arrest ended in dismissal. Between 2000 and 2011, about 13 percent were dismissed. And fewer murder or manslaughter charges — down from 6 percent to 4 percent — end up getting reduced to lesser offenses, such as obstruction of justice or carrying a pistol without a license.

Measuring progress

The historic drop in homicides to a 49-year low and the rise in case closures have been heavily publicized by city officials. The reduction in homicides has helped change the image of the city, once known as the murder capital of the country.

Lanier credits the improvement to several police practices: building better community ties, developing sources of information, using modern technology, enforcing information-sharing within law enforcement and focusing on violent repeat offenders. She also touts efforts to put more patrol officers on the streets to address crime hot spots. She points out that calls to the police tip line have increased from less than 300 in 2008 to more than 1,200 last year, according to the department’s annual report.

“Our positive results can be attributed to proactive patrol measures and a collaborative approach with partners in the community and the criminal justice system,” she said in her end-of-the-year message. “A key to success was convincing all partners that we could prevent the next homicide through immediate and coordinated action.”

Under Lanier, the statistics used by the department to measure homicide success have soared.

Each year, the department submits to the FBI’s Uniform Crime Reporting Program the number of slayings that occur in the city, along with the number of homicide cases closed that year, regardless of the year the killing occurred. Cases can be closed with an arrest or administratively without an arrest, including instances in which the suspect is dead or already incarcerated.

Since the UCR rate includes closed cases that originated in earlier years, it can theoretically exceed 100 percent. In the past decade in the District, the UCR closure rate has increased from 49 percent in 2001 to 94 percent in 2011.

A second measure used for calculating homicide performance, which counts only cases closed in the same year that they happen, has also gone up, from a low of 34 percent in 2001 to a high of 57 percent in 2011, the Post study showed.

Despite the positive trends, getting witnesses in killings can still be a struggle.

“You get a lot of shooting scenes where everybody knows everybody, and now they’ve all got hidden biases or they’ve got internal fears about cooperating with the police that make it exceedingly difficult,” said Jeffrey Ragsdale, homicide section chief for the U.S. attorney’s office in the District. “I honestly do think the police do the best they can with whatever they have, and I think they try to bring it to us as soon as they can. And then it’s us trying to do the best with their product.”

D.C. homicide detectives have complained for years that a lack of cooperating witnesses has hampered their ability to solve murders.

“Your case is only as good as your witnesses,” said longtime detective Tony Patterson. People often “have that mentality, ‘I don’t want to snitch,’ ” he said. “They just don’t want to be labeled a snitch.”

“It’s frustrating when . . . they’re telling you they know who did it but nobody’s willing to come forward,” Patterson said. “They say they’re scared until you bring them in. Then they say they don’t want to be a snitch.”

At least 15 witnesses appear to have been executed since 2000, according to The Post’s analysis of police homicide records. Lanier said that only five of those cases have been confirmed as witness killings. But records from the U.S. attorney’s office identify at least seven others.

Constance Smith said she believes a man got away with killing her son, Donta Baylor, because witnesses were afraid to testify.

“Basically, no one came forward in the case, because he was intimidating to the people in the neighborhood,” Smith said of the suspect.

Baylor, 29, was shot and killed as he descended the front steps of a female friend’s apartment in the 3500 block of Sixth Street SE shortly before 4:30 a.m. on June 3, 2004. Police records classified the motive for the shooting as “drug-robbery.”

Nearly six months later, police arrested a 23-year-old man with no fixed address and charged him with murder while armed, possession of a firearm, and robbery. In March 2006, prosecutors dismissed the charges because of insufficient evidence, according to William Miller, a spokesman for the U.S. attorney’s office.

“They told me they would charge him at a later date,” said Smith, who sat behind the suspect in the hearing at D.C. Superior Court. She said she is “still wondering what happened.”

Even when witnesses surface, cases can fall apart.

Sharon Wallace still cannot believe that prosecutors dismissed the case of the man accused of killing her husband.

Elwood Wallace, 52, was a street vendor who operated in the 2800 block of Good Hope Road SE. One sunny, brisk March afternoon in 2009, Sharon Wallace drove by her husband’s stand and noticed a gaggle of police officers.

She stopped her car in the middle of the street, got out and craned her neck. Her husband of nearly 20 years was slumped over his stand of hats, belts and oils.

“I knew he was dead,” Wallace recalled in an interview. “I couldn’t believe it.”

Two witnesses told police that they saw a man come up behind Wallace, shoot him in the back of the head and flee on foot, according to records. They both identified the gunman. Police closed the case the next day with the man’s arrest, charging the 54-year-old with first-degree murder, possession of a firearm during a crime of violence, carrying a pistol without a license and possession of a weapon by a felon.

In July 2010 — 16 months later — the U.S. attorney’s office dismissed the charges without trying the case. Prosecutors have declined to discuss the case, which authorities described as a “dispute shooting.”

“I couldn’t believe they dismissed the case,” Wallace said. “It definitely was wrong.”

Miller said the case “remains under investigation.”

Reducing homicides

Over the past 20 years, D.C. police have made myriad attempts to reduce homicides and raise closure rates.

In the early 1960s, the number of homicides in the District never surpassed 100 a year. As the nation’s homicide rate grew, so did the city’s, though it stabilized in the 1970s.

But slayings soared when the crack cocaine epidemic took hold of the District in the late 1980s. By 1991, they were at 482. The homicide rate was the highest in the United States, earning the city the title “murder capital of the country.” Detectives and prosecutors were overwhelmed with a high caseload, resulting in the dismissal of scores of cases in D.C. Superior Court.

Isaac Fulwood Jr., who had been named police chief in July 1989 by Mayor Marion Barry (D), beefed up the homicide unit. Federal and elected city officials had increased the department’s budget by $100 million, ordering the chief to hire 1,500 new officers in less than 24 months.

But the killings continued unabated.

Fulwood resigned in September 1992, and Mayor Sharon Pratt Kelly (D) tapped Fred Thomas. With homicides at 454 in 1993, Thomas asked his homicide commander, Capt. W. Louis Hennessy, to reduce the numbers. Hennessy had detectives specialize in geographic areas.

“At that time, we had so many retaliatory shootings . . . that it just made sense to get the guys immersed in these neighborhoods,” Hennessy recalled in a recent interview with The Post. “I was taking the community policing philosophy and extending it to homicide investigations.”

Homicides dropped to 361 in 1995, but UCR closures also dropped, to a low of 38 percent, according to UCR records. Hennessy blamed it on a decision by the D.C. Council to cut officers’ overtime. “It just made it very, very difficult,” he said. “I couldn’t let guys work on cases anymore beyond their tour of duty.”

By then, Barry was mayor again and Larry D. Soulsby had become the new chief. At the suggestion of a consulting firm, Soulsby decentralized the homicide unit, sending detectives out into the seven district stations.

But a Justice Department review of hundreds of D.C. homicides from 1991 through 1994 found that cases were going unsolved because of poor police work by homicide detectives. Soulsby resigned in November 1997, and the District then put its money on a little-known outsider from Chicago.

Charles H. Ramsey, who spent 30 years in the Chicago Police Department, had a reputation for being a community builder. Ramsey took over in April 1998 and immediately redeployed 300 detectives in specialized squads to the seven districts, making them responsible for all cases involving property and violent crime.

Homicides began dropping in the District and around the country in the late 1990s, with the District ending 1999 with 241 homicides. But the closure rate remained low and a year-long investigation by The Post published in December 2000 found fundamental flaws in the cases, including hundreds of missing and incomplete files.

Ramsey vowed to make improvements.

“The criminal investigative process is bad,” Ramsey told the D.C. Council in January 2001.

In October 2001, Ramsey re-centralized the homicide unit in hopes of closing more cases. When he resigned in 2006 after more than eight years with the department, Ramsey left the agency with a 65 percent UCR closure rate. Homicides stood at 169, the lowest in more than 20 years.

Last year, the number of cases fell to 108, and the UCR rate hit 94 percent. Included in that rate was the closure of 41 homicide cases dating back to 1989. Fifteen of those closures were made administratively without an arrest.

Dan Hill contributed to this report.