WCXX

Los Angeles (CNN) -- Negative headlines about drugs and sex abuse charges greatly diminished Michael Jackson's earning potential, an entertainment consultant said.

Jackson's album sales dropped sharply from his peak and his "likability" rating turned dramatically negative after "significantly negative headlines, drug abuse and other issues," Eric Briggs testified.

Briggs' testimony in the wrongful death trial of AEG Live is intended to counter an expert hired by Jackson lawyers who concluded the pop icon would have earned another $1.5 billion from world tours had he not died while preparing for his comeback concerts.

AEG Live placed a big bet on Jackson's ability to sell tickets when it signed him to a three-year deal for his "This Is It" tour. While the company worked hard to convince Jackson in 2009 to let them produce and promote the concerts, it paid Briggs more than $700,000 to prepare testimony for this trial questioning Jackson's star power.

In fact, AEG Live executives bragged at the time about how Jackson's first 50 London concerts sold out in record time with enough potential buyers lined up to sell out another 50 shows.

If a jury decides that AEG Live is liable for Jackson's death, his lost earnings potential would factor into their determination of damages to be paid by the concert promoter.

Michael Jackson's drug use explored in trial

Michael Jackson's mother and three children are suing AEG Live, contending it negligently hired, retained or supervised the doctor convicted of involuntary manslaughter in his death.

AEG Live lawyers argue that Jackson, not their executives, chose and controlled Dr. Conrad Murray and that they had no way of knowing about the dangerous treatments he was giving Jackson in the privacy of his bedroom.

They contend the singer was so deceptive and secretive about his medical treatments and drug use that even his family did not know. To help make their case, they'll play video of Jackson's youngest brother Randy being questioned about it. His testimony is expected to be shown to jurors after Brigg's testimony is concluded Wednesday.

Jackson's oldest sister Rebbie and ex-wife Debbie Rowe are also lined up to testify in the coming days. AEG Live is compelling their testimony, hoping to get revelations about Jackson's drug use.

Tuesday marks the 59th day of testimony in the trial, which the judge said could take another six weeks in a Los Angeles courtroom.

MJ's Q score

Briggs testified that he studied "Q score" data for Jackson, the trend of his album sales and his stability to conclude that Jackson had a low chance of earning money from endorsements and sponsorships.

An entertainment industry analyst hired by Jackson lawyers testified he was "reasonably certain" Jackson would have earned $300 million from endorsements and sponsorships.

Briggs disputed the estimate, saying that while Jackson was "a great performer" companies decide which celebrities to align their products with based on "likability" as measured by "Q scores."

Jackson's "Q score" in 1993 was in line with the average male musical performer, with about one person of every two surveyed saying they liked him, Briggs said. That was the year Jackson announced he had a problem with painkillers, and he entered rehab.

His score became dramatically negative over the next decade, Briggs said. By 2006, a year after he was acquitted in a child molestation trial, more than seven people said they disliked Jackson for every one who said they liked him, Briggs testified.

Companies would be "very anxious" about putting someone with such negative "likability" next to their products, he said.

Jackson lawyer Brian Panish will have a chance to question Briggs about his conclusions Tuesday.

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