Schoolgirl Ana Kriégel died from blunt force trauma to her head and neck, the Central Criminal Court has been told.

Former State Pathologist, Professor Marie Cassidy, gave evidence of the cause of death at the trial of two teenagers for the schoolgirl's murder.

The two 14-year-old boys deny the murder. One of the boys also denies carrying out a violent sexual assault.

The two accused boys were not present during Professor Cassidy's evidence.

Mr Justice Paul McDermott told the jurors that applications had been made to excuse their attendance during her testimony and he had granted those applications.

He said they were represented by their lawyers and parents.

Prof Cassidy told the court she had gone to the room in a derelict farmhouse in Lucan where Ana Kriégel's body was found on 17 May 2018.

She said there were obvious injuries to her head and neck and deep wounds to the 14-year-old's scalp.

Her body was covered in dust and dirt.

Prof Cassidy said her impression was that Ana had received severe injuries in the room in an area close to the doorway and her body was then moved or dragged further into the room.

She told the court there was a strip of tape loosely encircling the deceased's neck. She gave evidence of carrying out an external examination of the body. She said there were severe, extensive injuries, mainly to Ana Kriégel's head and neck and she identified around 60 areas of injury on her head and body.

Prof Cassidy said the cause of death was blunt force trauma to the head and neck. The injuries to the head were associated with some damage to the skull and bleeding to the brain which could have caused her death. The injury to Ana's neck would also have caused a lack of oxygen and could also have caused her death.

Prof Cassidy said there were four separate impacts to the right side and back of the deceased's head. She said they could have been caused by a fairly heavy object with a small striking surface or the corners of a larger object. She said the injuries to the face were different from those on the scalp.

The court was told the injuries to the head and neck would have rendered her unconscious and either or both could have caused her death.

The jury was also told there were numerous scratches to the 14-year-old's trunk and limbs. Some may have been caused in a struggle, Professor Cassidy said, and some could have been caused by moving her body across the rubble on the floor of the room. She said bruises on the arms and hands may have been defensive and could indicate a struggle.

Prof Cassidy said said her examination suggested she had not been sexually active and she could not say if injuries had been caused by consensual sexual activity.

She said it was possible she may have been unconscious or otherwise restrained when they occurred.

Under cross examination by lawyers for Boy A, she agreed these injuries were minor and said such injuries would be expected in someone who had not been sexually active, even in the context of consensual intercourse.

Prof Cassidy agreed under cross examination by lawyers for Boy B that injuries to Ana's neck could have been inflicted by someone putting an arm around her neck.

She agreed it was "a very horrific death".

Asked by Defence Counsel Damien Colgan, for Boy B, if someone observing this could suffer trauma, she said "anyone witnessing something like that would be traumatised".

Boy B was 'doing a good turn for a mate' - Kriégel murder trial hears