Dr. Metzger, Jackson's former physician, testifies during the Dr. Conrad Murray involuntary manslaughter trial in Los Angeles
Dr. Allan Metzger, Michael Jackson's former physician, testifies during the Dr. Conrad Murray involuntary manslaughter trial in Los Angeles, California October 24, 2011. Murray has pleaded not guilty and faces four years in prison and the loss of his medical licenses if convicted of involuntary manslaughter in singer Jackson's death. Reuters

The defense witnesses took stand on Monday, Oct. 24 at the the involuntary manslaughter trial of Michael Jackson's doctor, Dr. Conrad Murray.

Dr. Allen Metzger, the pop icon's longtime physician, testified that when he visited Jackson on April 18, 2009, the singer asked some intravenous sleep medicine, which referred to propofol.

According to Metzger, he didn't discern which kind of medication the singer wanted and he didn't give it to Jackson.

Metzger said he knew Jackson for about 15 to 20 years, and the King of Pop had long suffered from severe insomnia that is hard to be easily treated with various medicines. “Many medicines just did not work,” Metzger said.

Cherilyn Lee, a nurse practitioner, also took the stand on Monday also, saying that Jackson had asked her for propofol but she refused to provide it.

The defense attempted to suggest that Jackson was familiar with propofol and he could have administered it by himself to solve his severe insomnia.

According to the previous testimony of the defense, Murray had been trying to stop the King of Pop from using this powerful drug, which the star called milk. Instead, the doctor replaced the anesthetic Propofol with Lorazepam and Midazolam, for he was worried that the singer would be addicted.

The defense case is expected to comprise 15 witnesses in all until Oct 28.