The report from the medical examiner who conducted Prince’s autopsy is tantalizing for what it doesn’t say.

The single-page document lists a self-administered, accidental fentanyl overdose as the cause of death, but it offers few clues to indicate whether the musician was a chronic pain patient desperately seeking relief, a longtime opioid user whose habit became an addiction or a combination of both.

Blanks for contributing causes are marked “na” for “not applicable.” A space for “other significant conditions” is also marked “na.”

Authorities probably know much more than they are willing to discuss publicly as they seek the source of the fentanyl and consider criminal charges. For now, details in the report, combined with what’s known about Prince’s final days, hint at a fuller picture.

Among those details is a note that Prince’s body had scars on the left hip and right lower leg. The report doesn’t say, but it’s possible the scars were evidence of past surgeries for joint pain. At least one friend has said Prince suffered years of hip and knee pain from his athletic stage performances.

In many ways, the 57-year-old superstar fit the description of a chronic pain patient who got hooked on opioids, said Andrew Kolodny, director of Physicians for Responsible Opioid Prescribing.

Opioids lead to tolerance, and some patients seek out stronger drugs after initial dosages stop working.

Less than a week before Prince died, his plane made an emergency stop in Illinois on a flight back to Minnesota following a concert in Atlanta. The Associated Press and other media organizations, citing anonymous sources, reported that first responders gave him an antidote commonly used to reverse suspected opioid overdoses.


What is Fentanyl?

Fentanyl is a powerful, synthetic opioid prescribed by doctors to patients who develop a tolerance to other narcotics. It’s also a street drug with ties to labs in China that produce fentanyl equivalents for global distribution. Patients who have built up a tolerance to other prescription painkillers sometimes seek it out, and it is partly responsible for a recent surge in overdose deaths in some parts of the US. Because of its risks, it is tightly controlled by the Food and Drug Administration, but much of it is manufactured illegally.

Heroin-spiked fentanyl is marketed with brand names such as “China White” or “Fire.”

“Users know this and request it by name,” said Drug Enforcement Administration (DEA) spokesman Lawrence Payne.

“Was it a lozenge? Was it a skin patch?” said Dr Yashpal Agrawal of the College of American Pathologists. What’s more, there are numerous ways to misuse and overdose on fentanyl, by applying multiple skin patches or eating one, Agrawal said.

The report says nothing about other drugs Prince may have been taking. Some prescription drugs can affect the way fentanyl is processed by the body, increasing its toxicity, Agrawal said.


How do users get hold of it?

Nothing in the report explains whether Prince used a pharmaceutical product or a street drug. The report is silent on whether it was prescribed by a doctor or obtained illegally.

Kent Bailey, head of the DEA in Minneapolis, said the agency will continue investigating along with Carver County authorities and the US Attorney’s Office. He declined to offer details, but said “rest assured, we will be thorough.”

Legal experts say the focus of the investigation will now probably turn to whether the source or sources of the fentanyl were legal or not. Often, such investigations include grand jury subpoenas for records or for testimony from individuals.

Authorities may also look to the singer’s associates.

“The investigation may expand to people who surround him,” said Gal Pissetzky, a Chicago-based attorney who has represented multiple clients facing drug charges who has no link to Prince. “If fentanyl was obtained illegally, I don’t think Prince would have gone out to meet someone in a dark alley to get the substance.”

If a street dealer was the source, identifying that person won’t be easy.

“It’ll be very, very difficult,” he said. “These guys don’t write receipts, and they change phones all the time.”

Illegally distributing fentanyl to someone who then dies from it is punishable by a mandatory minimum sentence of 20 years under federal law. Under Minnesota law, the same actions can result in third-degree murder charges and up to 25 years in prison.


Who else is involved?

The names of at least two doctors have come up in the death investigation.

Dr Michael Todd Schulenberg, a family practitioner, treated Prince twice in the weeks before his death and told investigators he prescribed medications for the singer, according to a search warrant that did not specify which medications.

Schulenberg saw Prince April 7 and April 20 — the day before his death — according to the warrant. Schulenberg’s attorney, Amy Conners, said the doctor was interviewed by investigators April 21, right after Prince’s death, but has had “no further requests from investigators” since. She declined to comment further.

Dr Howard Kornfeld, a California addiction specialist, was asked by Prince’s representatives on April 20 to help the singer.

Kornfeld sent his son Andrew on a flight that night, and Andrew Kornfeld was among the people who found Prince’s body the next morning, according to Kornfeld’s attorney, William Mauzy.

The younger Kornfeld, who is not a doctor, was carrying a medication that can be used to treat opioid addiction, Mauzy said, explaining that Andrew Kornfeld intended to give the medication to a Minnesota doctor who had cleared his schedule to see Prince on April 21.

Mauzy has refused to identify that doctor. Schulenberg is not authorized to prescribe buprenorphine.

On Thursday, Mauzy said his clients never delivered, dispensed or administered any medication to Prince. The Kornfelds “were simply trying to help,” he said.