The ruling by Superior Court Judge Rodney Melville was a victory for the news media and the prosecution, which both opposed a defense request to take up the matter behind closed doors.
"I was very pleased that the judge recognized the California Supreme Court ruling that hearings such as admission of evidence be held in open court," media attorney Theodore Boutrous Jr. said.
The judge said he will schedule the arguments after the jury is selected.
Jackson was not present Wednesday. The 46-year-old pop star is charged with plying a boy with alcohol and molesting him. Jury selection begins Jan. 31.
Jackson's lawyers had contended that holding a open hearing on the alleged prior offenses would influence prospective jurors.
The judge has also ordered TV correspondent Martin Bashir to come to California to testify in the trial on March 1. Bashir produced the 2003 TV documentary in which Jackson said that he let children sleep in his bed but that it was not sexual.
Bashir is now a correspondent for ABC News, which said Wednesday it will fight the subpoena.
"We feel strongly that the California shield law protects the rights of journalists who cannot be — or be perceived to be — arms of either the prosecution or defense as they pursue the news," ABC News Vice President Jeffrey Schneider said.
"This is an effort on the part of the prosecution to introduce evidence of other claims of molestation against Michael Jackson," CBS News legal analyst Trent Copeland told The Early Show co-anchor Julie Chen. "These former boys -- or these young men at this stage -- are probably victims or alleged victims, according to the prosecution, who have also claimed they've been molested by Michael Jackson.
"Now, the prosecution, strangely enough, really only intends to call one of those victims, according to the defense, although they intend to introduce evidence that he molested all of them. So this is a risky strategy.
"I think if it works, clearly it could be a devastating blow to the defense, and I think the results of this ruling will resonate throughout this trial."
Maureen Orth, a special correspondent for Vanity Fair who will be covering the Jackson trial for the magazine, agrees, telling Chen, "It's crucial what happens (Wednesday), because really, the defense strategy is to destroy the credibility of this current accuser and his family. And if the prosecution can show that many of these things were actually part of a pattern, it certainly helps their case."
Orth says prosecution wants to show "there's a real pattern of behavior here, a modis operandi, that there's striking similarities between the 1993 case in which a young boy was paid off, over $25 million when it's all added up, and this current case – plus, there's a lot of special friends in between. So the prosecution wants to show that what this young boy is alleging is not an isolated case -- this is something that's been going on for decades."