He may have had access to a bottle of propofol without Murray knowing, the appeal says.
"Jackson was very familiar with propofol, as other doctors had administered propofol to him," Wass writes. "It is conceivable that Jackson had obtained a secondary source for the drug, especially because Jackson had been receiving nightly infusions from appellant for the previous two months, and appellant had Sunday nights off."
If Jackson -- not Murray -- administered the final and fatal dose, then it was not the doctor's fault the patient died, the argument says.
Murray's appeal disputes the prosecution argument that Murray was criminally liable even if Jackson had administered the fatal dose himself because Murray should have known that leaving the drugs near Jackson's bed posed a risk. The risk was "not reasonably foreseeable," it said.
The prosecution will have a chance to respond to Murray's arguments before the California appeals court makes a decision.