Updated: 18.35

David Mahon's murder trial has heard that a post mortem was not able to confirm whether Dean Fitzpatrick ran onto a knife or was stabbed.

A pathologist has told David Mahon’s murder trial that the fatal knife wound suffered by his stepson wasn’t a “gutting” as described by the prosecution.

Dr. Michael Curtis described the injury as “non-survivable” but said he couldn’t confirm whether there was a run on the blade or a deliberate thrust.

The 45-year-old denies murdering his stepson outside his apartment at Northern Cross, Malahide in Dublin in May 2013.

Before evidence of the post mortem was heard, the public gallery was warned the details could be distressing, particularly for family members.

Dean's mother Audrey, who is married to the accused, stayed away from the courtroom for this part of the trial.

Dr Michael Curtis said an internal examination revealed a 7cm horizontal slice across the stomach which continued right through to the bones of his spine - a depth of 14.2cm.

Dr Curtis said it cut through the body's main blood vessel, causing a significant loss of blood. He described it as an injury that was essentially non-survivable.

Mr Mahon is accused of stabbing his stepson following an alteration over the theft of a water bottle from his bike. Afterwards, he told gardaí that Dean walked onto the blade after he took it from him.

On pathology grounds, Dr Curtis said he was not in a position to determine whether there was a run-on the blade or a deliberate thrust.

The trial continues before a jury of six men and six women.

Newstalk's court correspondent Frank Greaney spoke to Newstalk Breakfast earlier about what happened in court yesterday.