Lawyers for Michael Jackson and his family on Sunday prepared to square off in a courtroom hearing over control of the singer's estate as media reports mounted about powerful drugs that may have contributed to his death.

One legal expert predicted the existence of a 2002 will signed by Jackson means his mother, 79-year-old Katherine Jackson, will likely be forced to give up temporary control she now has over his affairs.

"Given the existence of the will and the expression of Michael's intentions, the only likely outcome is Katherine's powers will be terminated and she will no longer have any power to deal with the estate," Los Angeles-based family law attorney Michael G. Dave said on Sunday.

Lawyers for Katherine Jackson and for two men named co-executors of the will -- attorney John Branca and music executive John McClain -- that surfaced late last week will meet in Los Angeles Superior Court on Monday.

Katherine Jackson was granted temporary administrator of her son's affairs last week before the will became known.

It puts his estate, which in an attachment is valued at more than $500 million, into a family trust that benefits his three children, his mother, and charities.

Jackson died as much as $500 million in debt according to media reports, but he had assets that have been valued as high as $1 billion and include part ownership in a music catalog of songs from the Beatles and other recording artists.