Nancy Kerrigan: Dad Was My Brothers' Ultimate Role Model

Speaking out for the first time since her father's Jan. 24 death, Olympic figure skater Nancy Kerrigan said her dad was her "safety net" and that "the last several weeks have been the most difficult of my life."

Nancy's brother Mark Kerrigan, 45, is accused of strangling Daniel Kerrigan, 70, the night he died and has pleaded not guilty to assault and battery charges.

But today, Nancy Kerrigan painted a different picture of her brothers' relationship to their father, writing: "For my brothers, he was the ultimate role model: the guy they continue to try to emulate."

"Mark adored his father and is grieving over his death," Mark Kerrigan's attorney, Janice Bassil, told ABC News. "I am grateful to the family for wanting to support Mark."

Death Ruled a Homicide'

On Tuesday, Daniel Kerrigan's death was ruled a homicide by the state medical examiner, according to Middlesex, Mass., District Attorney Gerry Leone. Mark Kerrigan now could face more serious charges, according to legal experts.

In her letter today, Nancy Kerrigan maintained that her family was a united front, saying, "It isn't over yet, particularly with the ruling this week about the cause of my dad's death; a ruling by the way which we think was unjustified and which we plan to help my brother fight."

The examiner's report found that Daniel Kerrigan died from cardiac dysrhythmia, a heart rhythm problem, following a fight in which he suffered a neck compression that fractured cartilage in his larynx, Leone said. But Kerrigan also had preexisting hypertensive and atherosclerotic cardiovascular heart disease, according to the report.

"When someone has underlying heart disease, strangulation can cause a lack of oxygen and a surge of adrenaline, either of which can precipitate a fatal heart irregularity," cardiologist Dr. David Lee told ABC News.

Kerrigan was found face down and unresponsive after the alleged attack, and his son was "clearly intoxicated," police sources told ABC News. There was blood near Kerrigan's body and pictures were knocked off the wall, according to police reports.

Mark Kerrigan was living in his parents' basement and had a long history of drinking problems, law enforcement sources said.

Kerrigan Family Stands by Mark

Brenda Kerrigan, Kerrigan's wife and Mark and Nancy's mother, maintained her son's innocence, claiming that Kerrigan died from a heart attack, not from the fight.

In today's letter, Kerrigan wrote that to her mother, Daniel Kerrigan "was her eyes, her confidante, her dance partner, her life partner. In short, he was her everything."

"We pray daily for our brother Mark that he will receive the help he needs and be reunited with the family soon," her letter added.

Kerrigan family attorney Tracy Miner also backed Mark Kerrigan.

"The Kerrigan family is extremely disappointed that the medical examiner would release a cause of death without having all of the relevant facts," Miner said. "The Kerrigan family does not blame anyone for the unfortunate death of Dan Kerrigan, who had a pre-existing heart condition."

Bassil told ABC News that she wants to review the autopsy report with an independent expert and has "a lot of questions as to whether whatever occurred between Mark and his father is the cause of his father's death."

Possible Murder or Manslaughter Charges for Mark Kerrigan?

The homicide ruling could prompt new charges of murder or manslaughter against Mark Kerrigan, legal experts said. Prosecutors could charge murder if there is evidence that he intended to kill his father, or manslaughter if it is determined that his acts were reckless enough to lead to death.

Both would require proof that Mark Kerrigan's alleged attack caused his father's death. Despite the homicide ruling, cause of death would ultimately be decided by a jury.

"I am guessing there will be a battle between medical experts on both sides," criminal defense lawyer David Duncan said.

"The prosecution will have an uphill battle because of the inability of any medical expert to define the actual cause of death without engaging in speculation," according to Veronica J. White of White & Associates, P.C.

Kerrigan's pre-existing heart condition makes causation even harder to prove, White added.

The Middlesex district attorney's office would not comment on whether it will bring new charges, saying only that the investigation "remains ongoing."

Mark Kerrigan is being held at Bridgewater State Hospital, where he is undergoing psychiatric evaluations. He is scheduled to be back in court for a probable cause hearing on Feb. 24.