Los Angeles (CNN) -- Michael Jackson died because Dr. Conrad Murray failed to notice that his patient had stopped breathing while he was hooked up to an IV drip of the surgical anesthetic propofol, an expert anesthesiologist testified Thursday. Dr. Steven Shafer, probably the last witness before the prosecution rests in Dr. Murray's involuntary manslaughter trial, said Murray should have realized Jackson had stopped breathing about 11:45 a.m. on June 25, 2009. "When you're there, you see it, you know it," Shafer said. Phone records and testimony showed that Murray was on the phone with one of his clinics, a patient, and then a girlfriend about the time that Shafer calculated the oxygen in Jackson's lungs became depleted, causing his heart to stop beating.
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NEW: A doctor demonstrates IV drips he believes killed Michael Jackson
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NEW: Murray could've saved Jackson if he was watching him, prosecution expert says
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"It's just a crazy scenario," doctor says of defense theory Jackson gave himself propofol
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Murray's lawyers should start their defense Friday
After the defense cross-examination of @placeholder on Friday afternoon, Murray's lawyers will start calling witnesses, including their own anesthesiology expert.