People vs. Dr. Conrad Murray -- Addiction Expert: MJ Was Dependent On Demerol

Addiction expert Dr. Robert Waldman -- the defense's penultimate witness -- said Michael Jackson became physically dependent on the pain killer Demerol in the months before he died.

Waldman said Jackson received "unusually large" amounts of the highly-addictive drug during at least 24 visits to his dermatologist between March and June, 2009.

Waldman also said one of the symptoms of withdrawal from the drug is insomnia... a condition MJ was known to suffer from.

Defense attorney Ed Chernoff went over medical records from MJ's dermatologist -- Dr. Arnold Klein -- which showed each time Jackson went in for a botox and anti-perspiration treatments -- relatively painless procedures -- he got a boatload of Demerol.

MJ started his "treatments" in March 2009 ... getting 200 mg of Demerol per visit. By May, he was receiving 300 mg.