"I've never seen my brother have any different, abnormal behavior that would ... any substance that would cause that. I've never seen this, so I would say 'no,'" Jackson said in a candid interview with French television.
Jermaine Jackson also tearfully scolded the media for the intense scrutiny his brother's death and custody battle have undergone.
"Leave him alone. Stop the crazy names that they call him," the Gloved One's brother said. "What more do you have to do to make people realize he's a human being? They need to leave him alone."
Despite Jermaine Jackson's comments, E! Online reported both Michael Jackson's autopsies included needle marks on the body and traces of the sedative propofol in his system.
This week the Los Angeles Police Department and federal agents followed leads in Las Vegas amid reports Michael Jackson consulted with doctors there.
To retired LAPD detective Robert Jakucs, the investigation is unfolding at the perfect pace.
"There is no timeline in this type of investigation," Jakucs said. "Police are doing this by the numbers. Because there's a celebrity involved, they're not going to make this any faster."
As far as the battle over Michael Jackson's children and estate, Jermaine Jackson said his brother's will should be the final word.
"The will is what it is. It's the will from my brother. Anybody that tried to contest this will on any level, whether it's with executors, or whether it's with anything, they're not living out Michael's wishes," he said.
The fate of Michael Jackson's children and personal assets may remain unsettled for some time, but sources say the fate of his professional swan song may be nearing a resolution.
Sources tell ABC News that Sony may be close to closing a deal to pay up to $50 million for the rights to Jackson's final performance video, to be compiled from 100 hours of rehearsal footage owned by concert promoter AEG.
"We're told that Sony pretty much has the deal," Sharon Waxman, editor of the Wrap Web site, told "Good Morning America" today. "I mean, the T's aren't crossed and the I's aren't dotted on the paperwork, but our understanding is the deal's done."
Michael Jackson died June 25 of apparent cardiac arrest at his rented Los Angeles mansion. Police are tryiing to determine whether powerful prescription drugs contributed to his death.
Jackson's This Is It Tour would have reportedly brought in at least $165 million, but that number may be exceeded, now that he's gone.
That's because AEG is also selling television rights to a September tribute concert that reportedly included major headline acts, possibly the Jackson brothers.
As for Jackson's share of the Sony/ATV music catalog -- more than 700,000 songs that comprise some of the Beatles most popular music --- it could be worth upward of $1 billion if Jackson's estate ever sells.
But who controls all that money is still up for debate. While TMZ reported this morning that Katherine Jackson's attorney, Londell McMillan, is planning to challenge estate executors John Branca and John McLain, McMillan issued a statement Monday that said Katherine simply wants to keep her options open.