His attorney, Vincent DiFabio, had sought a 72-hour jail sentence, standard for first-time offenders, noting that O'Neill was helping to care for a handicapped son.
But Mahon's sentence was at least 20 times that. "He deserved it," said Assistant District Attorney Marilyn M. Seide.
At the sentencing hearing this afternoon, one of O'Neill's counselors, Jeffrey Walder, described him as "great kid." DiFabio also provided several written testimonials to O'Neill's character.
"I want to take the opportunity to apologize to everyone," O'Neill said in a statement, breaking down several times. Seide handed him a box of tissues.
"That's the first time I heard him say that," said Susan Sheridan, mother of Scott Sheridan, whom O'Neill accidentally shot and killed at an underage drinking party in 2006.
Susan Sheridan was angry that she wasn't permitted to testify. She said it wasn't fair that someone was allowed to attest to O'Neill's character and that she didn't get a chance to talk about her deceased son.
Mahon said O'Neill's wasn't a typical drunken-driving case. "In Sean's situation, he has a very unique background," he said.
After the death of Scott Sheridan, a search of the family's home in Willistown Township resulted in a federal firearms conviction of his father, wealthy former bar owner Sean Owen O'Neill Sr.
O'Neill, an undocumented immigrant was deported to Ireland after serving an 18-month jail term.
Another of the family's three children, Roisin O'Neill, was involved in a 2008 Blue Route crash while she was intoxicated that killed that killed Patricia Murphy Waggoner, 63, a grandmother from Brimfield, Mass.
Sean O'Neill Jr. was sentenced today for a crash that occurred just before 1 a.m. last Thanksgiving.
Police said he was driving in on Westtown Road in West Goshen ad when he lost control of his black Cadillac, which ran across a yard and hit the garage of the house next door. No one was injured, police said.
"Are you one of those 'poor me' people?" Mahon asked O'Neill.
"You're blaming the alcohol.
"It's you."
Contact Anthony R. Wood at 610-313-8210 or twood@phillynews.com
