Dr. Timothy Botello, an expert in psychiatry, said Dr. Khristine Eroshevich was excessively prescribing drugs to the late celebrity model in amounts that could have been dangerous.
In examining records of the case, Botello said he could find no medical reasons to prescribe the dosages of four different medications being given to Smith simultaneously by Eroshevich toward the end of her life.
"For someone with a drug addiction history, it would be quite dangerous," he said.
"Is it your opinion that Anna Nicole Smith was an addict?" asked Deputy District Attorney Sean Carney.
"Yes, based in the information I reviewed," he said during an ongoing preliminary hearing.
Smith died at a Florida hotel in February 2007 of an accidental overdose of at least nine different medications.
Eroshevich, Dr. Sandeep Kapoor and Smith's former boyfriend-lawyer Howard K. Stern are charged with conspiring to illegally provide Smith with controlled substances. The allegations include giving drugs to an addict.
All three have pleaded not guilty. They are not charged in the death of Smith.
The preliminary hearing is being held to determine whether there is enough evidence to order them to stand trial.
Botello testified that Smith's medical records showed she had been treated for addiction at the Betty Ford Center before she met Eroshevich, and that she had been admitted to Cedars-Sinai Medical Center in 2006 to withdraw from drugs when she was pregnant.
Botello said he didn't know if Eroshevich was aware of either hospitalization or if she was conferring with other doctors who had been treating Smith for years for chronic pain.
"Given the history of substance abuse, you would be careful to give the lowest amount" of drugs, he said.
A psychiatrist prescribing medications in the situation should have been part of a pain management team, conferring with other doctors to assure they did not duplicate prescriptions, he said.
Botello said he assumed Eroshevich and Kapoor knew each other. But Kapoor has said he never met Eroshevich while both were treating Smith.
Testimony indicated Eroshevich began her relationship with Smith as a friend and neighbor. Botello said that made it doubly important that she separate the personal and medical relationships while prescribing drugs.
Testimony suggested that Eroshevich was trying to help Smith recover from the 2006 death of her son, Daniel, when she began prescribing sedatives.
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By Linda Deutsch