The judge who sent Lindsay Lohan to jail removed herself from the case after a prosecutor complained she improperly contacted experts or participants in the case.
Superior Court Judge Marsha Revel recused herself last week, a court spokesman said.
Beverly Hills Superior Court Judge Elden Fox is now handling the Lohan case.
Revel's clerk said there would be no comment.
District attorney's office spokeswoman Jane Robison said there were several instances when the judge held private communications and the prosecutor was not present or told afterward.
In one instance, the judge contacted the Morningside Recovery rehab facility, which was not on a list provided by her court-appointed experts. She then selected Morningside as a place to send Lohan.
Lohan's attorney Shawn Chapman Holley eventually persuaded the judge to send Lohan to Ronald Reagan UCLA Medical Center.
An email request to Chapman seeking comment was not immediately returned, and court officials declined to comment further.
The actress was released August 2 from the women's jail in Lynwood, where she served 14 days of a 90-day sentence for violating her probation in a 2007 drug case.
She immediately went to the UCLA drug rehabilitation facility for a court-ordered three-month stint.