The woman took the stand in a hearing at which Jackson's defense is seeking to exclude evidence seized from the private investigator's office on grounds of attorney-client privilege, as well as some items taken from his Neverland Ranch during a search.
The 36-year-old woman, who had allowed her children to make overnight visits to Neverland, made the sign of the cross after entering the courtroom. She glanced briefly at Jackson, 46, who stared at her throughout her testimony. She did not look back at him.
The testimony was the first time since the case began that the accuser's mother came face to face with the pop star, whom she had called "the devil" at a grand jury hearing earlier this year.
Jackson, dressed in a white suit with an embroidered gold armband, was greeted with cheers from dozens of fans when he arrived at the Santa Barbara County courthouse. One fan held a banner with a picture of the pop star and others hoisted signs saying "We Love You Michael."
One woman supporting the prosecution held a sign that read: "We Support the Victim."
Outside court, Jackson attorney Thomas Mesereau Jr. proclaimed: "The charges he faces are false and will be battled in a court of law within our justice system. He is innocent and will be vindicated."
Jackson's attorneys are trying to show that the accuser's mother and prosecutors should have known private investigator Bradley Miller was working for Jackson's then-attorney Mark Geragos when authorities seized items from Miller's office.
During questioning of the woman, Mesereau referred repeatedly to a transcript of an interview between Miller and the mother Feb. 16, 2003, just days after her young son appeared with Jackson on a television special.
Mesereau noted the transcript said Miller told her at the beginning and end of the interview that he was a private investigator working for "specifically an attorney named Mark Geragos who works for Michael Jackson."
She would not answer directly when Mesereau repeatedly asked if the document was false.
"I'm not denying it was said. I'm saying I don't remember," she testified.
The woman said she believed Miller was Jackson's private investigator because someone named "Frank" had told her so before she met Miller. She did not further identify "Frank."
Mesereau occasionally seemed exasperated when the woman said she didn't understand some of his questions. When he asked if Miller had told her he worked for Geragos, she repeatedly said of Miller, "He's your guy."
On Thursday, Jackson's defense attorneys played video recordings of the Neverland search, arguing that law enforcement officers overstepped their bounds by taking items not covered in a search warrant.
Jackson has pleaded not guilty to child molestation, conspiracy and administering an intoxicating agent, alcohol.