In a ruling that could boost federal efforts to prosecute athletes who used steroids, a US appeals court said yesterday that lower courts had wrongly blocked the US government from access to confidential Major League Baseball drug tests.

At issue are subpoenas involving more than 100 baseball players in tests by two laboratories. Prosecutors continue to investigate whether players such as Barry Bonds, who holds the record for home runs in a single season, lied to a federal grand jury in San Francisco about steroid use.

A three-judge panel of the 9th US Circuit Court of Appeals in San Francisco said a lower-court judge who had overseen cases involving Balco, a San Francisco-area lab that illegally distributed steroids to athletes, had abused her discretion.

“The subpoenas were not unreasonable and did not constitute harassment,” Judge Diarmuid O’Scannlain wrote for the panel. The drug tests could provide key evidence in showing which players used steroids, drugs many observers see as behind an explosion of home runs in the late 1990s and early 2000s. Amid growing scrutiny in recent years, Major League Baseball started unannounced steroid testing of players in 2003.

Michael Rains, criminal attorney for Bonds, said the tests did not incriminate his client, who could become the major leagues’ all-time home-run king next season.

“If what the government saw and got in April of 2004 was harmful to Barry Bonds, you can darn well bet that would have been leaked by now,” he said in an interview. “There is nothing at all about those tests that is harmful to Barry Bonds.”

“The government’s quest to get these — initially I’m sure just to target Barry — has been just another of a goose egg for them in their continuing efforts to both target, harass, indict and prosecute Barry Bonds.” US Attorney Kevin Ryan said in a statement, “We are pleased that the majority of the 9th Circuit panel found that the government’s seizures and use of grand jury subpoenas were reasonable.”

“We will continue to review the ... opinion to determine what the next investigative step may be,” Ryan said.

Investigators initially obtained a subpoena in 2003 to receive the anonymous drug testing results for 11 baseball players, and then sought to get the results from two firms that did the work, Quest Diagnostics in New Jersey and Comprehensive Diagnostic Testing, or CDT, in Long Beach, California.

A legal fight ensued and federal agents in April 2004 searched CDT, finding positive drug test results for eight players, with possible positive results for 26 others, according to the court ruling.

The government sought further records amid opposition from the labs and the Major League Baseball Players Association. A different judge in Nevada ordered the return of specimens and notes. That ruling was also wrong, the 9th Circuit said.

In a partial dissent in the 115-page ruling, Judge Sidney Thomas expressed concern the ruling would ease the way for prosecutors to seize confidential medical records.

“There is no question that the baseball players who participated in the random testing had a justified expectation of privacy in the test results,” Thomas wrote.

“The scope of the majority’s new holding in the digital age could not be greater; it removes confidential electronic records from the protections of the Fourth Amendment.”

A spokesman for Major League Baseball declined comment, saying lawyers had not yet reviewed the decision.