Dr. Conrad Murray Trial: A former patient of Dr. Conrad Murray says the doc saved his life

(CBS/AP) LOS ANGELES - A former patient of the doctor charged in Michael Jackson's death told jurors the physician saved his life.

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Robert Russell of Las Vegas lauded Dr. Conrad Murray's treatment of him, but testified Friday that his cardiologist became increasingly distant and hard to reach while working with Jackson.

Russell told jurors he couldn't get answers about his treatment from Murray's office on June 25, 2009 and demanded to speak to the doctor. The doctor left him a voicemail at 11:49 a.m.

Prosecutors are using records to show that Murray was on the phone in the moments before he realized Jackson was unconscious.

Russell told jurors Murray's message seemed odd because the doctor said he was going on sabbatical, despite telling the salesman and his wife months earlier that he was going to work for Jackson.

Murray, 58, has pleaded not guilty to a charge of involuntary manslaughter. If convicted, Murray could face up to four years in prison and lose his medical license.

Jurors are expected Friday to hear from paramedics who responded to the singer's rented mansion and tried to revive him.

Complete coverage of the Michael Jackson - Dr. Conrad Murray case on CBS News