The negligence of his doctor is the proof of murder. The doctors dosage had killed Michael Jackson, and that would be considered manslaughter because he was medically negligent when using the drugs that he administered. He may not have had been killed in the essence of a hit man per se, but was still killed.
While one could argue that the doctor prescribing the medication was compensated for in essence killing Michael Jackson, just like a hit man, but this analogy is false. The doctor simply did something that was unfortunately irresponsible. If you crash your car and kill someone while speeding or running a light, you are doing the same, but I'd hardly consider that murder.
No, I do not believe that Michael Jackson was murdered. Michael Jackson's doctor may have partially contributed to his death, but I do not believe that this means he was murdered. There was no malicious intent involved and I don't believe that manslaughter and murder should be considered the same thing.
Goodness gracious. No, he wasn't murdered. He had a lot of problems to begin with, couple that with a doctor that is out to lunch and you're going to inevitably have a sad ending to the story. That's all that occurred here, there was no plot to get rid of him.