Why didn't police seal the mansion where he had been living? Why were moving vans seen at the home, and were any items removed before police wrapped up their search? Why didn't they get immediate search warrants? Why did they tow away a doctor's car right after the death but not declare the home a crime scene?
Los Angeles police say proper procedures were followed based on the circumstances officers encountered when they were called to the home at 12:21 p.m. on June 25. A doctor was attending to Jackson and stayed with him when he was placed in an ambulance at 1:07 p.m. There was no sign of foul play.
Others say police should have assumed it was possible a crime occurred and taken precautions to ensure the scene was not disrupted so evidence wasn't lost or tainted.
"If I was the chief detective on the case, I would have said, 'We don't know what's going on. We should seal the scene,"' said defense attorney Harland Braun, who has represented celebrities including Robert Blake, Roseanne and Gary Busey. "You always have to think of the worst-case scenario and you have to think fast. I would have sealed the scene just because it was Michael Jackson."
Whether the Jackson probe turns into a criminal investigation hinges on what evidence emerges involving the drugs. Charges could be brought if authorities determine Jackson had been overly prescribed medications, if he had been given drugs inappropriate for his medical needs, or if doctors knowingly prescribed Jackson medications under an assumed name.
It's still not known what caused Jackson's death at age 50. The pop star went into cardiac arrest in his bedroom and his personal physician, Dr. Conrad Murray, performed CPR while an ambulance was called, according to Murray's lawyers. Murray has spoken to police and authorities say he is not a suspect, though his actions have come under scrutiny because his own lawyers acknowledge it may have taken up to a half-hour for an ambulance to be summoned.
An autopsy was conducted but results are not expected for several weeks. The Jackson family had a second autopsy performed and those results also are pending.
On Wednesday, The Associated Press learned Los Angeles police asked the Drug Enforcement Administration to assist in the investigation.
DEA agents participated in the investigation of the 2007 overdose death of Anna Nicole Smith at a Florida hotel. California Attorney General Jerry Brown investigated her former boyfriend and two of her doctors.
Brown handed the investigation over to the Los Angeles district attorney's office, which filed charges of conspiring to provide Smith with prescription drugs.
Brown said the suspects broke the law because Smith was a "known addict." The former boyfriend and doctors denied the charges.
The DEA also probed whether painkillers found in actor Heath Ledger's system after his death last year were obtained illegally. Federal prosecutors did not charge anyone.
Jean Rosenbluth, a University of Southern California law professor, said the agency's involvement in the Jackson case suggests authorities are looking into whether drugs came from out of state. Murray lives in Las Vegas and is licensed to practice in Texas, Nevada and California.
Federal drug regulations include controls over whether and how frequently a doctor can write prescriptions over the phone, and DEA agents could be looking to see if these rules were broken, Rosenbluth said.
"You can't just get on the phone and continue to prescribe something for someone without having seen them for a long period of time," she said.
Jackson had a well-known history of using prescription medications, especially painkillers. Following his death, Cherilyn Lee, a registered nurse who had worked for Jackson, told the AP she repeatedly rejected his demands for the drug Diprivan, also known as Propofol. It's a potent anesthetic used in operating rooms and it would be highly unusual to have it in a private home.
Uri Geller, a former Jackson confidant, said he tried to keep Jackson from abusing painkillers and other prescription drugs, but others in the singer's circle kept him supplied.
"When Michael asked for something, he got it," Geller said in a telephone interview from his suburban London home.
Jackson had multiple doctors and many others like Geller who came in and out of his life. Which people are being interviewed by police is unclear because the LAPD has said virtually nothing about the probe.
"I am not going to make any comments on the investigation," Commander Patrick Gannon, the designated police spokesman on the Jackson case, said by e-mail Thursday.
Any evidence would be turned over to the district attorney's office, which has final say on criminal charges.
One of the key questions is why it took four days for police to issue a search warrant and remove medications from Jackson's home.
Although the home wasn't declared a crime scene, police did tow Murray's car the evening of the death to look for potential evidence.
Vernon J. Geberth, former commanding officer of the Bronx Homicide Task force in New York, said police should have known they were dealing with an extraordinary situation.
"If it's a high-profile person, you have to do more than you would do ordinarily," he said.
Still, Geberth, who now acts as a private forensic consultant, said he believes the LAPD acted appropriately.
"Having a doctor present altered the equation. It was not a homicide scene. It was an emergency medical scene," he said.
Police spokesman Lt. John Romero declined to comment when asked if the LAPD was reviewing its handling of the investigation.
Rosenbluth said if the case ends up as a criminal prosecution, any defense attorney would seize on the LAPD's failure to immediately seal Jackson's home.
"If you can get even one juror think, I don't know, maybe somebody fiddled with the medicine before the police came in and collected it, that's reasonable doubt," she said. "All that the defense attorney needs is one juror."