An in-depth investigation by the Philadelphia Inquirer has revealed a 20-year long practice by the city's police department of burying rape reports. The extensive cover-up led to thousands of cases being hidden without investigation-and thousands of rapists getting away with their crimes.

For two decades, the Philly police sex crimes unit "buried their cases, rejecting a remarkably high proportion of reported rapes as 'unfounded' and deliberately miscoding others to keep the department's crime numbers artificially low," the Inquirer found.

One of the rape cases that police dismissed is now linked to a serial rapist who murdered a subsequent victim; the confirming DNA test was conducted only after repeated requests from the Inquirer.

Philadelphia's sex crimes unit was started in 1981 to counter the department's tendency to poorly treat rape victims. Ironically, the new unit made things even worse.

"With pressure from the top to show results, too few investigators and a huge caseload, the unit became expert at getting rid of-or hiding-cases that could not be solved easily," the paper reported.

"Year after year, hundreds of cases were dumped in 'investigation of person,' an obscure administrative category meant for situations where no crime was committed. Cases put there do not show up in crime statistics" or receive investigation.

"The victims typically had no idea their cases had been mothballed. Many never heard from police after an initial hospital interview. Some who tried to prod investigators said their calls were not returned," the paper continued.

The Inquirer analyzed police reports, emergency room records, court files and FBI documents going back two decades. Their findings were reported in a two-part series this month.

Initially, the sex crimes unit classified many rapes as "unfounded," which is reserved for groundless crimes, when the "victim" is proven to be lying. In the first half of 1983, police dismissed 52 percent of rape complaints as fabrications; the national average was about 10 percent, according to the Inquirer.

"After the FBI privately raised questions about the practice in 1983, the 'unfounded' numbers dropped sharply almost overnight -not because sex-crimes investigators were taking women's complaints more seriously, but because they had found a new hiding place for them.

"It began putting hundreds of sexual-assault complaints in a bureaucratic twilight zone-Code 2701, 'investigation of person'-to keep them out of the city's crime statistics," said the Inquirer.

From the mid-1980s until last year, about a third of all rape complaints were categorized as "investigation of person." In 1996 and 1997, 2,000 of the 7,500 total reports were hidden in that non-crime category.

Two years ago the FBI and auditors again raised questions. Again, instead of changing behavior, the sex crimes unit just changed tactics. In 1998, the police stopped using Code 2701, but doubled to 18 percent those complaints listed as 'unfounded,' the paper found.

New police commissioner John F. Timoney admits the abuses happened and called the practice of misclassifying rapes "stupid." At the same time, Timoney refused to provide the Inquirer information about sexual assaults that may have been miscoded before 1998, when he took over the force.

The entire Philadelphia Inquirer series is available online at http://www.philly.com/packages/crime/.