The former model's friend and psychiatrist, Dr. Khristine Erosovich, is on trial along with two other defendants, Dr. Sandeep Kapoor and Smith's lawyer-boyfriend Howard K. Stern for conspiracy to furnish excessive drugs to an addict.
They are not charged in Smith's 2007 overdose death, which was deemed an accident.
In his final arguments, Bradley Brunon said Erosovich ordered sedatives as part of an "emergency mission" and that she was trying to help a friend, not get her high.
Erosovich was a friend and neighbor of Smith before she treated the former model for pain-related anxiety, stress and sleeplessness.
Brunon stressed Erosovich's medical board record in good standing and that she has no history of impropriety.
Kapoor's attorney, Ellyn Garafalo, defended the doctor saying his prescriptions were medically justified.
"A person whose drug-seeking behavior is for pain relief is not an addict," Garafalo told the jury. Kapoor and Stern were set to deliver their closing arguments after Brunon.
On Thursday, the defense will present its closing arguments for Stern, who allegedly joined the doctors in a conspiracy to overmedicate Smith.
Attorneys rebut the charge, telling the jury that the object of a conspiracy is to do something illegal, like robbing a bank or committing a murder. They said it's not a pact motivated by compassion.
On Tuesday, the prosecution concluded its closing arguments by accusing the defendants of supplying Smith with powerful painkillers despite clear signs of her addiction because they wanted to enhance their relationships with Smith and her celebrity world.
The Associated Press contributed to this report.