Prosecutors will be asking a Pima County Superior Court judge Friday to dismiss murder and child abuse charges against a Tucson couple accused of killing the woman’s 1-year-old son.

Paramedics were called to a home near East Grant Road and North First Avenue in July 2009 after Brett Dillon went into respiratory arrest. The police were told the baby had fallen in the bathtub and hit his head. He died two days later and his mother, Melissa Julie Bizilia, 22, and her boyfriend, Ryan Fitzgerald Sullivan, 34, were arrested and indicted.

Investigators determined the child was in Sullivan’s care and the injuries took place while his mother was at work.

The doctor who performed the autopsy originally said the boy died of blunt force trauma to the head but now says Brett could have died as a result of a heart ailment, according to court documents.

“While the state remains convinced that the defendants committed the offenses for which they have been charged, it has an ethical duty to explore the new evidence with due diligence,” prosecutors Fran Maffetone and Susan Eazer wrote.

They are in the process of having tissue samples analyzed, but because the case is two years old and the defendants have invoked their right to a speedy trial, a postponement of their Feb. 23 trial is inappropriate, Eazer and Maffetone wrote.

They have asked for the case to be dismissed without prejudice, meaning it could be refiled if new or additional evidence comes to light.

Judge Howard Fell will take up the issue tomorrow at 9 a.m.

Sullivan remains in jail on $500,000 bail. Bizilia’s bail was lowered from $500,000 to zero in September. She is currently living out-of-state and is required to stay in telephone contact with the county’s pretrial services division. She must also personally check in with the police chief of the community she is living in every Thursday.

Contact reporter Kim Smith at 573-4241 or