Mercer County Prosecutor Announces New Deputy First Assistant

MERCER COUNTY, NJ - Mercer County Prosecutor Angelo J. Onofri announced the promotion of Kathleen M. Petrucci to deputy first assistant prosecutor.

Petrucci was sworn in last week by the Hon. Peter E. Warshaw, J.S.C., at the Mercer County Criminal Courthouse.

Petrucci began her career as an assistant prosecutor in the Mercer County Prosecutor’s Office in September 1999. During her 24 years, she was assigned to the Trial Unit, Gang Unit, Project Safe Neighborhoods Unit, Juvenile Unit, Grand Jury Unit, Special Investigations Unit/Mercer County Narcotics Task Force, Internal Affairs Unit, and the Mercer County Homicide Task Force.

She has served as chief of the Juvenile Unit and chief of the Gang Unit. After four years as a trial team leader, Petrucci was assigned to the Special Investigations Unit and served as its chief from 2016-2018. She was also cross-designated as a special assistant U.S. attorney, and assigned to the U.S. Attorney’s Office in 2018-2019 to screen and adopt state drug and gun crimes from Mercer County. Recently, she has been the senior assistant prosecutor supervising the Mercer County Homicide Task Force.

During her career in Mercer County, Petrucci has conducted numerous jury trials arising from homicides, aggravated assaults, firearms possessions and drug distributions. Trials have included the attempted murder case of State v. Billy Heisler, who was convicted in 2012 of the attempted murder of an off-duty Mercer County Sheriff’s Officer and sentenced to 50 years in prison. Her more recent trial was the double murder case of State v. Treizon Thompson, who was convicted in December 2022 of the murders of two rival gang members.

While Petrucci will continue to prosecute homicide cases, in her new role her responsibilities will expand to include general oversight of the Major Crimes, Special Investigations and Appellate units, as well as assisting with formulating policy and overseeing investigations. She has served as an administrative assistant prosecutor since September 2021.

Petrucci graduated from Bethany College (WV) in 1992 and Seton Hall University Law School in 1998.