New D.C. Data Alter Violent Crime Tally

"This shows our system works," Ramsey said. "It is a good safeguard for accuracy."

The police department's research unit identified the problems, according to its director, Anne Grant. After reviewing stacks of written reports and matching them against the crime database, the unit found that large numbers of crimes were missing, Grant said.

"We're not sure why," Grant said.

Four audits in the past year have found thousands of discrepancies that are still being sorted out, she said.

In January, the department provided statistics showing that the number of violent offenses in 2006 was down 2.4 percent from the previous year.

The new totals continue to show a 14 percent drop in homicides and a 10 percent increase in sexual assaults, as previously reported.

The revised tally shows 4,453 aggravated assaults -- attacks, usually with a weapon, that are meant to cause severe bodily injury -- compared with 3,854 in 2005. And officials now say that the city had 3,604 robberies in 2006, up from 3,502 the previous year.

The revised numbers still pale in comparison with the volume of crime in the late 1980s and early 1990s, when crack cocaine was blamed for a surge in bloodshed. The city had 169 homicides last year, compared with 479 in 1991.

Lanier and other officials said the record-keeping problems stem in part from the department's use of two databases for crime statistics.

One database relies on clerks in each police district to input information at 4 a.m. each day. It is used by officials to form crime strategies and is also the information released to the public.

The second is maintained in a more methodical way, with researchers entering information from written police reports weeks or months after crimes occur. That database is kept to report information to the FBI each year.

One of Lanier's priorities is to automate police reports, eliminating paper, with one master database tracking crimes.

Once that system is in place, Lanier said, the information will be more accurate.