In the days leading up to Michael Jackson's (search) arrest on child molestation charges, the district attorney handling the case took the unusual step of personally conducting surveillance at the office of a private investigator working for the singer's lawyer, a defense request unsealed Thursday said.

The filing, made public a day before the next scheduled hearing in the pop star's molestation and conspiracy case, said police "invaded the defense camp" in a November search of private investigator Bradley Miller's office in Beverly Hills (search).

The defense said evidence taken from Miller's office should be returned to Jackson's attorneys because police had no right to seize it under attorney-client privilege, which bars the prosecution from learning about communication between Jackson and his attorneys.

The defense said law enforcement officers used a sledgehammer to enter Miller's office and conference room during the search.

The request, filed on June 22, asked Judge Rodney S. Melville not to allow the evidence, including videotapes and computer hard drives, to be admitted at trial.

The mention of District Attorney Tom Sneddon's (search) personal visit to the investigator's office was part of a continued attempt by the defense to portray him as overly zealous in his pursuit of Jackson.

In a document unsealed Wednesday asking that the grand jury indictment of Jackson be dismissed, defense attorneys said Sneddon was unusually aggressive in his questioning of one witness.

The defense request cited a memo by Sneddon that said he had visited the building where Miller's office was located, photographed a list of offices there, and climbed the stairs to the second floor in an unsuccessful search for Miller's office.

Prosecutors responded that they had no evidence that Miller was working for Mark Geragos, who was Jackson's attorney at the time of the search but left the case in April.

They also said the office of a lawyer or private investigator could be searched if prosecutors had reason to believe it held evidence not covered by attorney-client privilege.

Also Thursday, media attorney Theodore Boutrous Jr. filed an appeal notice with the California 2nd District Court of Appeals challenging the pattern of secrecy that has surrounded the Jackson case.

The filing said news organizations including The Associated Press were appealing a long list of orders issued by Melville that sealed such items as search warrants, grand jury transcripts and key sections of the indictment. The organizations are also appealing the practice of holding of secret hearings in the case without public notice.