Irish nanny Aisling Brady McCarthy has been detained without bail after appearing at a court near Boston on charges of first-degree murder, assault and battery, causing the death of one-year-old Rehma Sabir in January.

Judge Thomas Billings refused to release her on bail of $5,000 dollars given the nature of the charges, and on the basis that she was a foreign national with international ties.

34 year old Ms Brady McCarthy pleaded not guilty to the charges when she appeared before the court in the Boston suburb of Woburn in Massachusetts.

She spoke just three times during a court hearing that lasted more than an hour.

The Cavan native, who now lives in Quincy, has lived in the US for about 13 years and worked illegally as a nanny.

Ms Brady McCarthy appeared tearful and upset and tried to hide from the view of the public gallery.

Her defence lawyer Melinda Thompson insisted that Ms Brady McCarthy was innocent. “This is homicide" she said," but the wrong person has been charged with this crime.”"