The ruling came after Superior Court Judge Robert Perry chose to throw out the 2010 jury verdict that manager Howard K. Stern and psychiatrist Khristine Eroshevich conspired to obtain prescription drugs for the troubled model by using false names.
The judge found it was not unusual in the celebrity world Smith inhabited for fake names to be used to protect privacy.
The Second District Court of Appeals reversed those findings, saying there was enough evidence to support the conspiracy convictions. It said Stern cannot be tried but Eroshevich might get another trial.
Lawyers called the decision confusing.
Stern and Eroshevich were convicted Oct. 28, 2010, in the case of the reality TV star and former Playboy model, but the bulk of the charges against them were thrown out at their sentencing hearing.
In September of last year, prosecutors filed an unusual appeal saying Judge Perry was biased and abused his discretion when he dismissed the few counts on which Stern and Eroshevich were convicted.
A jury previously acquitted them on most of the 11 charges involving drug prescriptions given to Smith in the months before she died in Florida on Feb. 8, 2007, of an accidental drug overdose. The defendants were not charged with causing her death.
The two guilty verdicts against Eroshevich and Stern on conspiracy counts involved the use of false names to obtain prescription pain medications for Smith. Eroshevich also was convicted of one count of obtaining Vicodin under a false name.
Perry dismissed the conspiracy counts and reduced the one conviction against Eroshevich to a misdemeanor with a sentence of one year probation.
Prosecutors argued in the appeal that Perry was biased against them and had created a celebrity exception to the law. They noted that Perry accused a prosecutor of ethical violations during the case and said that the case had been overcharged.
Perry suggested authorities had chosen the wrong case to prove their point and indicated they did not understand the legislative intent of the law involving prescription drugs.
A co-defendant, Dr. Sandeep Kapoor, who was Smith's physician, was acquitted of all charges.
The defendants' nine-week trial was the final act of the long-running drama centering on the blonde beauty's troubled life, which was documented on reality TV, in tabloids and in trial testimony.