Katherine Jackson has "made it her mission" to take Dr. Conrad Murray "down".
The Jackson family matriarch is upset with the medic - who served two years for the involuntary manslaughter of Michael Jackson, her son - after he made a series of embarrassing revelations about the star, including claims he was incontinent at night and had to have a catheter fitted to him before bed.
A source told Globe magazine: "He's a delusional liar who's only out for himself. Katherine's been hurt so much by this man and yet he continues to bring more and more pain.
"She has made it her mission to take him down. She will use the remainder of her life to ensure he pays dearly."
The source added Dr. Murray's giving interviews about Michael - who claims the late star told him they were like "brothers" - are also affecting Michael's children, Prince, 16, Blanket, 11, and Paris, 15, who is recovering from an apparent suicide attempt in June.
The insider said: "Paris has been doing much better and is getting the help and support she long needed. But she is still very frail and has a long way to go."
Paris' mother, Debbie Rowe, has also been critical of Dr. Murray, saying: "A Jackson fan will shot him dead .... and I'd buy the bullet."