Despite her opinion that her father is guilty, Somers said she was careful not to taint her sister's recollection of the day their mother died in case she was called to testify at the trial.
Last week, the MacNeill family's next-door neighbor, Kristi Daniels, told the jury that Ada came to her the day of her mother's death and said, "my dad needs some help."
When Daniels entered the home on April 11, 2007, she said she stood in the doorway of the bathroom where Martin MacNeill was with his wife, who was unconscious in the bathtub and whose skin was a "greenish pale" color.
"It all happened so fast," Daniels kept saying on the stand in the courtroom.
Less than two hours later, Michele MacNeill was pronounced dead.
MacNeill's defense lawyers said heart problems were a contributing factor in the death of the mother of eight.
The medical examiner has never determined a cause of death.