Experts say the amount of fentanyl found in Prince’s system was higher than any previous fentanyl-related fatality that had been documented before his death.
A toxicology report from Prince's autopsy shows he had what multiple experts call an "exceedingly high" concentration of fentanyl in his body when he died.
Prince was 57 when he was found alone and unresponsive in an elevator at his Paisley Park estate on April 21, 2016.
Public data released six weeks after his death showed he died of an accidental overdose of fentanyl, a synthetic opioid 50 times more powerful than heroin.
A confidential toxicology report provides some insight into just how much fentanyl was in his system.
The report says the concentration of fentanyl in Prince's blood was 67.8 micrograms per litre. Source: AAP
Experts who are not connected to the Prince investigation said the numbers leave no doubt that fentanyl killed him.
"The amount in his blood is exceedingly high, even for somebody who is a chronic pain patient on fentanyl patches," said Dr Lewis Nelson, chairman of emergency medicine at Rutgers New Jersey Medical School.
He called the fentanyl concentrations "a pretty clear smoking gun".
The report says the concentration of fentanyl in Prince's blood was 67.8 micrograms per litre, while the report explains that fatalities have been documented in people with blood levels ranging from three to 58 micrograms per litre.
The report also says the level of fentanyl in Prince's liver was 450 micrograms per kilogram, and notes that liver concentrations greater than 69 micrograms per kilogram "seem to represent overdose or fatal toxicity cases".
There was also what experts called a potentially lethal amount of fentanyl in Prince's stomach.
Dr Charles McKay, president of the American College of Medical Toxicology, said generally speaking, the findings suggest Prince took the drug orally, while fentanyl in the blood and liver suggest it had some time to circulate before he died.
Experts said there is no "lethal level" at which fentanyl can kill. A person who takes prescription opioids for a long time builds up a tolerance, and a dose that could kill one person might help another.
Search warrants released about a year after Prince's death showed authorities found numerous pills in various containers around his home.
A lab report shows many of the pills tested positive for fentanyl and other drugs. Information that has been released publicly indicates the source of those drugs has not been determined.
Last week, the lead prosecutor in the county where Prince died said in a statement that he was reviewing law enforcement reports and would make a decision on whether to charge anyone "in the near future".
