According to the defense, Michael Jackson was so desperate for sleep that he reached for a dose of the powerful sedative propofol and somehow ingested it on his own.
But in court on Thursday, Deputy District Attorney David Walgren presented a 100-milliliter vial that prosecutors say delivered the deadly dose of the anesthetic, and a fingerprint found on it matched Murray's left index fingerprint.
The doctor's prints were found, but Jackson's fingerprints were not found on anything - not on any bottle, IV bag or syringe.
The findings opened the door for a barrage of questions, and the defense attacked the collection and documentation of the evidence by coroner investigator Elissa Fleak.
Fleak admitted to moving evidence, saying, "I do agree that I should have photographed the flomazinil on the floor before I put it onto the table. Yes, in hindsight, I would have done that."
She testified that she never took a picture that showed the position of a key piece of prosecution evidence: A Jackson staffer said he saw a bottle of propofol inside a saline bag, what looked like a setup for a drip into Jackson's body. But no photo of that was available.
Defense attorney Ed Chernoff also pointed out to Fleak that she did not mention finding a bottle of propofol inside an IV bag until March 2011.
When the prosecution asked her about her report, she admitted that she inaccurately described some of the medical equipment found in Jackson's bedroom - she had misidentified two parts of a syringe.
But the biggest lapse of all was that she contaminated a piece of evidence. Fleak testified that at some point, she did not have her gloves on and left a fingerprint on a syringe.
"I don't know when that happened. I typically wear gloves," she said.
When Chernoff asked for Fleak's original notes, she said she typically destroys her notes after her reports are completed because the information is contained in the report.
The defense drew testimony to highlight that she collected the evidence on two different days, the day of death and then days later when an investigator told her to go back and search the closets. For at least two days, the doors of the house were left unlocked.
Chernoff tried to get her to admit to sloppy work.
"Ms. Fleak, would you agree with me that you made a substantial number of mistakes in your investigation of this case," Chernoff asked.
"No," she responded.
"You wouldn't. Well, would you agree with me that if you don't take notes, you don't keep your notes, that's bad investigation, that's bad investigative work," Chernoff said.
Walgren responded to the defense's attack by asking Fleak, "Have you done your best to accurately describe what you've seen and observed throughout this investigation?"
Fleak responded that she has.
Toxicologist Dan Anderson testified for most of the afternoon about drugs found in Jackson's body, including different levels of propofol.
"I performed the neutral analysis, and I detected propofol," Anderson testified.
Anderson will continue his testimony on Friday.Murray is on trial for involuntary manslaughter for Jackson's sudden death on June 25, 2009, at the age of 50. Prosecutors allege Murray tried to hide the fact that he had been giving propofol to Jackson.
Murray, 58, has pleaded not guilty and has denied any wrongdoing. If convicted, he could face up to four years in prison and lose his medical license.
The trial is expected to last five weeks, with Oct. 28 being the estimated last day.