During cross-examination of Nixon, the defense attorney asked Nixon if he was on methadone when he told police his version of the story.
He said yes, and admitted that he bought the four shovels used to bury the Sumners.
The defense argued that it was actually Nixon who was the mastermind in the deaths.
In addition to Jackson and Nixon, prosecutors have charged Jackson's girlfriend and Alan Wade.
Nixon faces from 52 years to life in prison, but will not be sentenced until the cases of the other three defendants are resolved.
Jackson's trial is scheduled to continue Friday at 10 a.m.
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- May 1, 2007: Prosecutors: 'Ringleader' Made 911 Call Posing As Dead Man
- April 30, 2007: Second Man Goes On Trial In Couple's Slaying
- September 15, 2005: Two Suspects In Missing Couple's Murders Extradited
- August 12, 2005: Missing Couple Murder Suspects To Be Tried In Florida
- July 26, 2005: Police: Missing Couple's Graves Dug Several Days Before Being Buried Alive
- July 20, 2005: Medical Examiner: Missing Couple Buried Alive
- July 19, 2005: Family: Missing Couple's Kindness Led To Their Believed Death
- July 17, 2005: Police Recover Bodies Believed To Be Missing Couple
- July 16, 2005: Police: Missing Couple Believed Dead
- July 15, 2005: Police Speaking With 'Persons Of Interest' In Search For Missing Couple
- July 13, 2005: Police Suspect Foul Play In Missing Handicapped Couple's Disappearance
- July 13, 2005: Missing Couple Feared Victims Of Foul Play