Mark Kerrigan was arrested on 24 January (10) after his dad Daniel Kerrigan was found unconscious in the kitchen of the family home in Stoneham, Massachusetts.
He pleaded not guilty to charges of assault and battery with a dangerous weapon on an elderly person and causing serious bodily injury.
The 45 year old was released from a local detention centre in Woburn, Massachusetts in February (10) after he posted $10,000 (£6,250) bail, under the conditions he would remain under house arrest at his mother's home, submit to alcohol and drug screening and receive mental health counselling.
Authorities then added a charge of manslaughter and Kerrigan was indicted for the additional crime by a Middlesex Superior Court Grand Jury on Thursday (08Apr10).
According to the Middlesex Chief Medical Examiner, Daniel Kerrigan died from cardiac dysrhythmia after suffering a neck injury during a physical altercation at his home. Reports also indicate Daniel Kerrigan suffered a cartilage fracture to the larynx area - exacerbated by heart disease.
The Kerrigan family has openly supported Mark Kerrigan through the investigation, stating his father had pre-existing heart conditions.
Kerrigan family lawyer Tracy Miner tells People.com, "I'm disappointed. Manslaughter is a more serious charge than involuntary manslaughter. And it will definitely be harder to prove. They have to establish that he acted recklessly knowing that he acted knowing he could cause serious injury or death."
The case continues.