The cross examination of Dr Steven Shafer came a day after the expert prosecution witness gave damaging testimony against Murray at his involuntary manslaughter trial in Jackson's 2009 death from an overdose of the drug propofol and sedatives.

Shafer had set up an IV drip system in court to suggest the way in which Murray might have wrongfully infused the powerful anesthetic propofol into the singer. But defense attorneys on Friday disputed whether such a system was ever used.

"You understand that when the police came to the scene, when coroner investigators came to the scene, they did not find an IV set such as that one?" Ed Chernoff, the lead defense attorney, asked Shafer on the witness stand.

Shafer admitted that a vented IV tube with a plastic spike -- such as the one he used in his demonstration for jurors -- was not found at the scene. But he testified that Murray still could have used one and easily balled up the tube and pocketed it before leaving Jackson's Los Angeles mansion.

Jurors have heard prior testimony that an IV pole, saline bags and propofol vials were among the items found in Jackson's bedroom after he died on June 25, 2009.

Murray has admitted that on the day Jackson died he gave the singer a relatively small dose of 25 milligrams of propofol for sleep. Defense attorneys are challenging the prosecution's argument that Murray could have administered as much as 40 times that amount of the drug afterward through an IV.

Defense attorneys have said that Jackson might have given himself an extra, fatal dose of propofol when Murray was out of the bedroom.

Murray, who has pleaded not guilty, faces a maximum sentence of four years in prison if convicted.