Nicole Alvarez told jurors hearing the involuntary manslaughter case that Dr. Conrad Murray had been treating Jackson for a year before his death. She says Murray introduced her to Jackson several times, including after the birth of the couple's young son.
Alvarez says Murray would frequently leave her apartment at night and return early the next day. She says she knew Murray was working as Jackson's personal doctor as the singer prepared for a series of comeback concerts.
Murray has pleaded not guilty in connection with Jackson's death.