Majella Holohan is set to take the witness stand at the Central Criminal Court before 21-year-old student O'Donoghue is sentenced for her son's manslaughter.
She will give an emotional victim impact statement, which the judge will take into account when deciding O'Donoghue's sentence.
It is widely expected that she will attempt to publicly refer to evidence gathered by the gardaí but not presented to the jury in the murder trial. However, she may be prevented from doing so either by the judge, or on objection by the defence counsel.
The written statement is handed to the judge Mr Justice Paul Carney in advance. It can be shown to the defence in advance so counsel can make any representations on behalf of their client.
Scores of newspaper, radio and television journalists are to attend the hearing, which is expected to last up to 90 minutes.
The Irish Examiner understands that contrary to media speculation, Majella Holohan will not be holding a press conference after the sentencing.
O'Donoghue's parents, Ray and Therese, will not be making a statement after the trial.
Legal experts told the Irish Examiner that Ms Holohan is entitled to speak in court and add to the statement but only within reason.
"I am sure the family will confine themselves to the trauma (of the death) and the consequences of the event. Victim impact statements are very emotive things. Generally victims don't go over the top. They tend to be measured and very genuine," said one.
Victim impact statements tend to concentrate on how a crime has affected them and their families, legal experts say.
O'Donoghue, of Ballyedmond Hill, Midleton, Co Cork, was convicted of manslaughter last year at the Central Criminal Court sitting in Cork.
The trial was told how O'Donoghue grabbed Robert around the neck on January 4, 2005, after the boy started throwing stones at his car.
O'Donoghue, a second year engineering student at Cork Institute of Technology, admitted manslaughter but denied murder. He was cleared of murder.
He told investigating gardaí: "It was an accident. I didn't mean it. It was an accident. I am sorry. He was like a brother to me."
He will be sentenced at the Central Criminal Court sitting in Ennis, Co Clare.