The defense team for Aisling Brady McCarthy, the Irish nanny accused of murdering her one-year-old charge Rehma Sabir, have stated that the cause of the toddler’s death remains unclear.

According to the Boston Irish nanny’s attorney, Melinda Thompson, they are still trying to determine whether Sabir died from complications brought on by a genetic disorder or from physical trauma induced by someone other than McCarthy.

Rehma Sabir was found unconscious in her crib and rushed to hospital with head injuries on January 14, 2013. She died two days later. McCarthy, a Cavan native who had been working as Sabir’s nanny, was accused of her murder and has pleaded not guilty. She has been in prison awaiting trial since then and has been denied bail due to her undocumented status.

After Sabir’s death, a medical examiner concluded that the toddler had died from head trauma as a result of being physically shaken. However, an autopsy also found bone fractures that pre-dated the time Sabir was under McCarthy’s care.

The Irish Times reports that Thompson is still “unsure what type of defense she will mount in the case against her client because defense experts have not yet had a chance to examine tissue samples taken from the child by a medical examiner and organs donated by the girl’s family following her death.”

She said that McCarthy has “been accused of such a horrible thing but she maintains her innocence” and is eager for the trial to begin.

Jury selection for McCarthy’s trial is expected to begin on April 22 in Middlesex County Superior Court outside of Boston.