LOS ANGELES (KABC) -- From behind bars, Michael Jackson's doctor said he won't testify in Katherine Jackson's wrongful death lawsuit against entertainment giant AEG, claiming it could incriminate him and hurt his appeal to overturn his conviction.

Dr. Conrad Murray spoke via phone with CNN'S Anderson Cooper on Tuesday night. During the interview, Murray also broke out into song, belting out "The Little Boy That Santa Claus Forgot" and drawing parallels with the lyrics and the hardships of his life.

"That song tells my story, that's how I grew up," Murray said. "I had no Christmases, I had no toys, I had nothing. I walked barefoot for years. But as I grew up, my heart has been whole and my heart says to help, and all I do is to give. I want to give."

Attorneys in the current lawsuit want Murray to tell the jury about the terms of his hiring and AEG's role. What is known already from Murray's criminal case is that an AEG attorney testified that there was a contract. However, it was said that the contract was not signed by all the required parties.

"An oral contract (in California) is valid as long as there is some performance," said Barry Edwards, a specialist in civil litigation.

In this case, the plaintiffs allege AEG knew Murray's role and had many discussion about Jackson's physical demands.

Murray is serving two years of a four-year sentence after being found guilty of involuntary manslaughter in the death of pop star Michael Jackson.

The case pits Katherine Jackson and the star's three children against AEG, which was promoting the concert the pop star was working on before his death in 2009.

The lawsuit seeks $40 billion in damages, claiming AEG negligently hired and supervised cardiologist Dr. Conrad Murray, who was convicted of administering the fatal dose of the anesthetic drug propofol.

AEG denies that they hired Murray and says they were not negligent.

Potential jurors continued filling out questionnaires Wednesday in advance of the civil trial, which may last up to three months.

AEG, in its defense, has listed Jackson's two children - Prince and Paris - on its list of 81 witnesses they may call to testify.