A 46-year-old man has lost his appeal against the severity of the sentence he received for killing his partner's son.

David Mahon was sentenced to seven years in jail for the manslaughter of his 23-year-old stepson Dean Fitzpatrick in May 2013.

Mr Fitzpatrick was stabbed in the abdomen outside the apartment his mother, Audrey, shared with Mahon at Burnell Square, Northern Cross on the Malahide Road in Dublin.

The court heard that the two men had been arguing about a missing part of a bicycle.

The State argued that Mahon was drunk and agitated and had intended to kill his stepson.  

Mahon claimed that the death was accidental and that Mr Fitzpatrick "walked into the knife" he was holding.

The jury found him not guilty of murder but guilty of manslaughter in June last year.

Mahon did not appeal his conviction but appealed the severity of the sentence.

However, this morning the Court of Appeal ruled that the sentence was not out of line with sentences in other cases that might be regarded as broadly similar.  

It found the sentence fell within the range available and dismissed Mahon's appeal.

Mr Fitzpatrick death was the second tragedy to befall the family. Mr Fitzpatrick's 15-year-old sister Amy Fitzpatrick went missing on New Year's Day 2008 as she walked home from a friend's house on the Costa del Sol in Spain. She has not been seen since.