WASHINGTON — The recording industry provided its most detailed glimpse to date Wednesday of the detective-style techniques it has employed to reduce music piracy over the Internet.

Using a technical procedure, the Recording Industry Assn. of America examined song files on a Brooklyn woman’s computer and traced their digital fingerprints back to the former Napster file-sharing service, which shut down in 2001. The RIAA, the trade group for the largest record labels, said it also found other hidden evidence inside the woman’s music files suggesting the songs were recorded by other people and distributed across the Internet.

The disclosures were included in court papers filed against the woman, fighting efforts to identify her, for allegedly sharing nearly 1,000 songs over the Internet. The recording industry disputed her defense that songs on her family’s computer were from compact discs she had legally purchased.

The RIAA’s latest court papers describe in unprecedented detail some sophisticated forensic techniques used by its investigators. These disclosures were even more detailed than answers the RIAA provided weeks ago at the request of Sen. Norm Coleman (R-Minn.), who has promised hearings into the industry’s use of copyright subpoenas to track downloaders.

For example, the industry disclosed its use of a library of digital fingerprints, called “hashes,” that it said can uniquely identify MP3 music files that had been traded on the Napster service as far back as May 2000. Examining hashes is a technique commonly used by the FBI and other computer investigators in hacker cases.

By comparing the fingerprints of music files on a person’s computer against its library, the RIAA believes it can determine in some cases whether someone recorded a song from a legally purchased CD or downloaded it from someone else over the Internet.

Comparing the Brooklyn woman to a shoplifter, the RIAA told U.S. Magistrate John M. Facciola that she was “not an innocent or accidental infringer” and described her lawyer’s claims otherwise as “shockingly misleading.”

The woman’s lawyer, Daniel N. Ballard of Sacramento, said the music industry’s latest argument was “merely a smokescreen to divert attention” from the related issue of whether her Internet provider, Verizon Internet Services, must turn over her identity under a copyright subpoena.

“You cannot bypass people’s constitutional rights to privacy, due process and anonymous association to identify an alleged infringer,” Ballard said.

Ballard has asked the court to delay any ruling for two weeks while he prepares detailed arguments, and he noted that his client — identified only as “nycfashiongirl” — has already removed the file-sharing software from her family’s computer.

The RIAA accused “nycfashiongirl” of offering more than 900 songs by the Rolling Stones, U2, Michael Jackson and others for illegal download, along with 200 other computer files that included at least one full-length movie, “Pretty Woman.”

“The source for nycfashiongirl’s sound recordings was not her own personal CDs,” the RIAA’s lawyers wrote.

The recording industry also disclosed that it is examining so-called metadata tags, hidden snippets of information embedded within many MP3 music files. In this case, lawyers wrote, they found evidence that others — including one user who called himself “Atomic Playboy” — had recorded the music files and that some songs had been downloaded from known pirate Web sites.

The recording industry has won approval for more than 1,300 subpoenas compelling Internet providers to identify computer users suspected of illegally sharing music files on the Internet.

The RIAA has said it expects to file at least several hundred lawsuits seeking financial damages as early as next month.

The 1998 Digital Millennium Copyright Act permits music companies to force Internet providers to turn over the names of suspected music pirates upon subpoena from any U.S. District Court clerk’s office, without a judge’s signature required.