(BANG) -Michael Jackson's mother insists Dr. Conrad Murray "killed" her son, despite the physician pleading not guilty to his involuntary manslaughter.

Katherine Jackson watched as the medic - who was with Michael when he died last June - entered his plea at Los Angeles Superior Court yesterday (08.02.10) and later insisted he had lied to the judge.

She said: "He's lying. He's guilty. Nobody was there but him. He's just trying to save his own behind. He killed him. He wasn't monitoring him."

Michael's sister La Toya also spoke out against Murray and insisted she will continue to fight for justice for the late 'Thriller' singer.

She said: "Michael was murdered, and although he died at the hands of Dr. Conrad Murray, I believe Dr. Murray was a part of a much larger plan. There are other individuals involved, and I will not rest and I will continue to fight until all of the proper individuals are brought forth and justice is served."

Murray - who, according to prosecutors, unlawfully, but without malice, killed Michael - was later released on $75,000 bail.

However, his lawyer Edward Chernoff fears his client will not receive a fair trial because of Michael's popularity.

When asked whether it would be possible to find an impartial jury, he replied: "It's going to be tough, but I think if we get the right jury, the right result will come in."

Murray is accused of giving Michael the powerful anaesthetic Propofol to help him sleep but which instead led to his death on June 25.

If convicted, Murray faces a maximum of four years in prison. (C) BANG Media International