LOS ANGELES — Conrad Murray wants a key piece of evidence tested which his lawyers argue could prove Michael Jackson injected himself with the drug that killed him.

Murray, who is serving a four-year prison sentence, is appealing last year’s involuntary manslaughter conviction in Jackson’s 2009 death.

A motion filed Monday by his lawyers asked an appeals court to order a test of the residue in a 100 milliliter bottle of propofol that prosecutors say contained the fatal dose of surgical anesthetic.

If it contains 10% lidocaine, then it would support prosecution expert Dr. Steven Shafer’s theory that Murray rigged up an IV drip using the bottle and then left the room, Murray’s motion said.

Shafer testified that lidocaine, which was found in Jackson’s blood after his death, was mixed with propofol to ease the sting of the drug as it entered a vein in Jackson’s leg.

“However, if the residue is 100% propofol, it would absolutely refute Shafer’s final contention that was used to prove an IV propofol infusion,” the motion said.

The defense theory was that a desperate Jackson, fearing that his comeback concerts could be canceled unless he found elusive sleep, self-administered propofol that Murray was trying to wean him off of. It contends that Jackson also swallowed eight lorazepam tablets while Murray was not watching.

Two requests by Murray’s lawyers to have the bottle tested after the trial were rejected by the trial judge, who ruled they should have asked for testing before the trial.

Murray’s lawyers argued the residue in the bottle, which the prosecution never tested, became relevant only at the end of the prosecution’s case” when Shafer “remodeled” his theory about how Jackson died.

“Dr. Shafer made a striking change in his rebuttal testimony, which occurred during the final minutes of the evidentiary portion of the trial,” Murray lawyer Valerie Wass said.

Murray told police he stopped using IV infusions of propofol to help Jackson sleep three days before his death, and that he only injected a small dose the morning he died.

“The amount of propofol Murray claims he gave Jackson does in fact comport with the amount of propofol found in Jackson’s blood at autopsy.” Murray lawyer J. Michael Flanagan said. “There was no propofol infusion on the morning of Jackson’s death. The analysis of the residue in Exhibit 30 will prove the truth once and for all.”

The motion asks the appeals court to order the Los Angeles County Coroner to either test the residue or hand it over to a private lab for testing.