Jackson Time of Death a Mystery

Law enforcement sources tell TMZ the L.A. County Coroner cannot pinpoint the time of Michael Jackson's death ... but paramedics say when they arrived they believed he was dead for at least an hour and maybe longer.

Dr. Conrad Murray's statement to LAPD detectives lays out a timeline in which Dr. Murray administered Propofol at 10:40 AM and then ten minutes later (10:50) he walked out of the room, went to the bathroom and returned two minutes later (10:52) to find Jackson was not breathing. He did not have anyone call 911 until 12:21 PM ... approximately an hour-and-a-half later.

Sources say cops are suspicious of Dr. Murray's account. They say when Dr. Murray was interviewed by them two days after Jackson died -- his lawyer by his side -- the doctor's account seemed "scripted."

So when did Jackson really die? Rigor mortis typically doesn't set in for at least 3 hours, and often longer. If rigor mortis has not set in, the only way to approximate time of death is by body temperature. Once a person dies, their temperature eventually rises or falls to the temperature of the environment. For example, if Jackson were in a 70 degree room, his body temp would drop to 70. The body temperature typically drops a degree to a degree and a half per hour, but it's dependent on the ambient temperature.

Here's the problem -- when paramedics arrived the room was sweltering. So Jackson's body temperature could register in the 90 degree range, even if he were dead for a long time. But we're told paramedics did not get a read on his body temp because they were busy performing CPR.

Bottom line -- it's possible Jackson could have been dead much longer than Dr. Murray said. There's no scientific way of knowing.