Investigator testifying about Conrad Murray's cell phone

(CBS/AP) LOS ANGELES - Prosecutors have called a computer forensic analyst to describe his investigation of the cell phone of the doctor charged in Michael Jackson's death.

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Stephen Marx previously testified that he found emails that defendant Dr. Conrad Murray sent hours before Jackson died on June 25, 2009.

Marx is also expected to testify about the recording of a conversation between Jackson and Murray that was extracted from the physician's iPhone.

Prosecutors played the recording during opening statements and a voice is heard speaking extremely slowly and slurring his words.

The audio was one of the previously undisclosed pieces of evidence against Murray, who has pleaded not guilty to involuntary manslaughter in Jackson's death.

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