Overview
Practice Areas
Litigation • Securities Enforcement • White Collar Defense & Investigations •
Jeffrey P. Mongiello is a Member in the CSG Law White Collar Defense & Investigations Group.
A former prosecutor, Jeff represents corporations and individuals facing high-stakes government enforcement actions, grand jury investigations, and criminal prosecutions. From managing sensitive internal investigations to defending state and federal prosecutions, he helps clients navigate and resolve investigative inquiries, litigation, and charges. Jeff excels at advocacy and briefing, drawing on significant appellate experience and multiple published decisions that reflect his skill with complex legal issues.
Known for sophisticated motion practice and appellate advocacy, Jeff has handled more than 50 criminal appeals, both as a prosecutor and defense counsel, in the New Jersey Supreme Court and Appellate Division, as well as the federal Courts of Appeals. His practice features a distinct focus on protecting a client’s Fourth Amendment and privacy rights from government intrusion into electronic devices and data. Jeff’s recent successes include pushing back against government overreach in some of New Jersey’s most high-profile white-collar criminal matters.
- Jeff was integral in crafting the trial and appellate briefing that secured dismissal of a state racketeering indictment against an attorney.
- He drafted critical briefs challenging an indictment and search warrant for personal electronic devices in an official misconduct prosecution, ending with the state dropping charges against the client.
- He drafted the crucial post-trial brief in another public integrity prosecution, leading the trial judge to enter a judgment of acquittal in favor of the client and preventing the prosecutors from allowing the jurors to deliberate.
Jeff also routinely appears as amicus curiae on behalf of clients, drafting “friend of the court” briefs on behalf of non-parties to a litigation who have an interest in a court’s ruling on the law.
Before CSG Law, Jeff served as an associate at a national law firm and a regional law firm, and as a judicial law clerk for both the Honorable Mary L. Cooper, U.S.D.J., U.S. District Court for the District of New Jersey, and the Honorable Anne M. Patterson, Associate Justice of the New Jersey Supreme Court.
Before entering private practice, Jeff was a New Jersey State Deputy Attorney General in the Appellate Bureau of the Division of Criminal Justice, where he represented the State before the Appellate Division and New Jersey Supreme Court. In this role, he successfully defended against a constitutional challenge before the New Jersey Supreme Court to the state’s judicial recall statute, which authorizes retired judges over the age of 70 to temporarily return to service. Jeff was recognized in 2015 with the Attorney General’s Award for Excellence in Trial Litigation for his role in a successful public corruption prosecution by twice securing reversals on interlocutory appeals of the trial court’s rulings.
Jeff earned his J.D., magna cum laude, from Seton Hall University School of Law, where he was Managing Editor of Seton Hall Law Review, his M.P.P. from the University of Maryland School of Public Policy, and his B.A. from the University of Maryland.
*Results may vary depending on your particular facts and legal circumstances.
Honors
- Included in New Jersey Law Journal, New Leaders of the Bar (2021)
- Included in The Best Lawyers in America® “Ones to Watch,” Criminal Defense: White Collar (2022-2023); Commercial Litigation (2021-2023)
- Selected to the New Jersey Super Lawyers – Rising Stars list, Criminal Defense: White Collar; Appellate; Civil Litigation: Defense; Class Action/Mass Torts: Defense (2022-2023)
- Recipient, New Jersey Attorney General’s Award for Excellence in Trial Litigation (2015)
Award Methodology
*No aspect of this advertisement has been approved by the Supreme Court of New Jersey.
Involvement
- New Jersey State Bar Association, Appellate Practice Committee; Criminal Law Section
- National Association of Criminal Defense Lawyers
- Association of Criminal Defense Lawyers of New Jersey
- New Jersey Ethics Committee, District VI (Hudson County) (2017-2025)
Education
- Seton Hall University School of Law (J.D., magna cum laude, 2011)
- University of Maryland School of Public Policy (M.P.P., 2006)
- University of Maryland (B.A., 2005)
Admissions
- New Jersey
- New York
- U.S. Court of Appeals, Third Circuit
- U.S. Court of Appeals, Fifth Circuit
- U.S. District Court, District of New Jersey
- U.S. District Court, Eastern District of New York
- U.S. District Court, Southern District of New York
Overview
Recent representative matters include:
- Secured dismissal of racketeering indictment against well-respected New Jersey attorney, who was aggressively pursued by the New Jersey Attorney General’s Office of Public Integrity and Accountability. In a published decision, the New Jersey Appellate Division, agreeing with the trial court judge, explained that the state’s indictment failed to allege any criminal conduct against client.
- Secured dismissal of indictment for public school principal, who was charged with multiple second-degree counts of official misconduct. After filing a motion to dismiss the indictment and a motion to suppress digital evidence obtained from a cell phone, the State prosecutors dropped all charges against the client and dismissed their own case.
- Secured judgment of acquittal for client after close of evidence in a case brought by the New Jersey Attorney General’s Office of Public Integrity and Accountability. Trial court judge found that the matter could not proceed to the jury for deliberation because no reasonable jury could have found the client guilty beyond a reasonable doubt.
- Secured dismissal of indictment alleging a $300 million securities fraud and conspiracy against client. After demanding a speedy trial and filing motions related to impeachment evidence of a key witness, the Government decided to drop all charges against the client rather than proceeding with the trial.
- Defended a diagnostic testing company in False Claims Act suit brought by the Southern District of New York. Before retention, the Government had obtained prejudgment writs attaching liens to $109 million dollars’ worth of property. Following a motion for reconsideration and to release the writs, presenting new arguments and new evidence in support, the judge reversed his prior decision and voided the liens and allowed the client to re-access their property.
- Obtained favorable non-criminal resolution for public servant charged by the New Jersey Attorney General’s Office of Public Integrity and Accountability for official misconduct, which requires a minimum five-year sentence in prison. After filing multiple motions, including a successful motion to suppress evidence obtained via an unconstitutional search warrant for a cell phone, the State relented in its pursuit and offered the client a plea deal of a misdemeanor, meaning non-criminal conduct.
- Authored amicus curiae brief before the New Jersey Supreme Court identifying errors in two model jury charges. The Supreme Court directed the Committee on Model Criminal Jury Charges to review and update the charges.
- Obtained diversionary, pretrial intervention for client indicted by the New Jersey Attorney General’s Office of Public Integrity and Accountability for allegedly making false representations in contracts with government entities.
- Obtained return of client corporation’s funds seized from a bank account by the U.S. Department of Homeland Security – Homeland Security Investigations (HSI) in a civil forfeiture action.
Recent published decisions include:
- State v. Norcross, 484 N.J. Super. 1 (App. Div. 2026)
- United States v. LabQ Clinical Diagnostics, — F. Supp. 3d — (S.D.N.Y. 2026)
- State v. Bragg, 260 N.J. 387 (2025) (amicus)
- United States v. Fluitt, 99 F.4th 753 (5th Cir. 2024)
- State v. Jones, 443 N.J. Super. 515 (App. Div. 2016)
- State v. F.W., 443 N.J. Super. 476 (App. Div. 2016)
- State v. Buckner, 223 N.J. 1 (2015)
- State v. Olivero, 221 N.J. 632 (2015) (amicus)
- State v. Smith, 436 N.J. Super. 556 (App. Div. 2014)
- State v. Buckner, 437 N.J. Super. 8 (App. Div. 2014)
- Caswell v. Green, 424 F. App’x 44 (2d Cir. 2011)
*Results may vary depending on your particular facts and legal circumstances.