Week two, day five, of Conrad Murray's involuntary manslaughter trial got under way Monday in Los Angeles, with emergency room doctors and Murray's girlfriends on the list of potential witnesses.

Monday's courtroom activity commenced with testimony by Dr. Richelle Cooper, the Ronald Reagan UCLA Medical Center emergency room doctor who pronounced Jackson dead.

Cooper's testimony began on Friday.

Read more: Defense Faces Uphill Battle in Week 2

Cooper testified that Jackson was clinically dead, when he arrived at the hospital. He did not have a pulse. Cooper also said Murray told her Jackson's cardiac arrest began after Murray gave him two doses of the sedative lorazepam, but Murray did not mention Jackson's use of propofol.

Thao Nguyen, a cardiologist and part of the emergency room team that worked on Jackson, is also a potential Monday witness. In a preliminary hearing in January, Nguyen testified that the ER team used a balloon pump to try to restart Jackson's heart, and that Murray appeared devastated when ER staff couldn't revive the singer.

CNN.com reports that three of Murray's girlfriends could also provide key evidence in the case. Cocktail waitress Sade Anding was reportedly on a phone call with Murray shortly before the medical emergency with Jackson began on June 25, 2009.

Read more: Juror Questionnaire for Conrad Murray Trial Rife With Drug and Celebrity-Related Questions

Anding testified during a preliminary hearing in January that she had been talking to Murray when he suddenly stopped responding to her. I didn't hear him on the phone anymore, Anding said. I heard commotion as if the phone was in a pocket and I heard coughing, and I heard a mumbling of voices.

Prosecutors believe this may have been the moment when Murray first realized Jackson had stopped breathing, and it fits into their timeline of how Jackson's death unfolded.

Another Murray girlfriend, Bridgette Morgan, is expected to testify that she spoke to Murray about 30 minutes before the Jackson emergency began, while Nicole Alvarez, the mother of Murray's youngest child, is expected to testify that her Santa Monica, California address was used to receive shipments of propofol Murray had ordered for Jackson.

The coroner ruled Jackson died of acute propofol intoxication, along with sedatives. Prosecutors contend Murray is criminally accountable for Jackson's death because, as the late singer's personal physician while he prepared for a series of comeback concerts, Murray recklessly administered the propofol and was negligent in properly monitoring Jackson during his use of the surgical anesthetic drug.

One face that will be MIA in the Los Angeles courtroom this week: Michael Jackson's mother, Katherine. CNN reports she took Michael Jackson's children -- Prince, Paris and Blanket -- to Montreal for the premiere of Cirque du Soleil's Michael Jackson: The Immortal World Tour.

Katherine Jackson is also expected to travel to Cardiff, Wales for the Oct. 8 tribute concert Michael Forever, which is scheduled to include performances by Smokey Robinson, Black Eyed Peas, Cee Lo Green, Gladys Knight, Leona Lewis and Christina Aguilera.