Superior Court Judge Robert Perry said he fears the defendants cannot get a fair trial if attorneys focus on Smith's cause of death.
Dr. Sandeep Kapoor, Dr. Khristine Eroshevich and Howard K. Stern have pleaded not guilty to conspiring to illegally provide the former Playboy model with opiates and sedatives. They are not charged with causing her death.
Defense lawyers contend their clients did not know Smith was an addict and that they tried desperately to save the depressed model in her waning years, including a period when she gave birth to a daughter and lost her grown son to a drug overdose.
Perry also said during the pretrial hearing that he doesn't understand why the case was not filed in Florida, where Smith died in 2007.
Opening statements are scheduled Wednesday in the trial expected to last three months.
Prospective jurors have already filled out 14-page questionnaires. They are set to return Monday for in-depth questioning.
Juror prospects were asked to disclose their own medical histories and drugs they have used. They also were asked if they believe celebrities have a right to privacy about their medical records.