Lippes Mathias Reinforces Government & State Attorneys General Investigations Practice with Four Additions

August 17, 2022 | Press Releases

Karl J. Sleight, Brian C. Mahoney, Joan P. Sullivan join Lippes Mathias as partners, Christian R. Flemming joins as an associate 

BUFFALO, N.Y. – Lippes Mathias LLP announced today the strategic additions of Karl J. Sleight, Brian C. Mahoney, Joan P. Sullivan and Christian R. Flemming to its Government & State Attorneys General Investigations Practice Team. Karl, Brian and Joan join Lippes Mathias as partners and Christian joins as an associate.  

As businesses, not-for-profits and even government officials face increased scrutiny from federal and state law enforcement and regulatory agencies, Lippes Mathias offers a team with diverse backgrounds and unique skillsets to support clients faced with government investigations, internal investigations, government audits, regulatory compliance, and white-collar investigations. The team is co-led by New York State’s former Attorney General Dennis C. Vacco in Buffalo, N.Y. and Michael G. Rossetti in the firm’s Washington, D.C. office. The seasoned group, comprised of former federal and state prosecutors and a former judge, is uniquely positioned to bring unrivaled insight into the world of compliance and investigations. 

“We grow in ways to best serve our clients. These additions make our Government Investigations Team one of the largest and most impressively credentialed in New York outside of New York City,” said Kevin J. Cross, managing partner, Lippes Mathias. “With a shared vision for what law firm culture and client service should be, Karl, Brian, Joan, and Christian are excellent additions to our growing team and provide significant benefit to our clients with their experience.” 

“The additions of Karl, Brian, Joan and Christian will enhance the experienced Government Investigations Team as well as our geographic reach,” said Dennis C. Vacco, partner, executive committee member and co-team leader of the Government & State Attorneys General Investigations Team. “Our team boasts a unique skillset, bringing together significant prosecutorial experience, including former Assistant United States Attorneys, Assistant District Attorneys, and Assistant Attorneys General, paired with a keen understanding of the needs and priorities of the private sector.” 

Karl J. Sleight focuses on providing legal counsel and strategic advice to clients that operate in highly regulated environments having an active government oversight component. Karl was recognized for his accomplishments in the field, when he was named to the City and State Law Power 50 which listed the “50 most powerful people in New York politics working in the law.” He assists clients among a broad spectrum of sectors including gaming, Title IX, health care and emerging industries. Karl represents individuals, businesses and institutions in complex civil litigation, government administrative investigations, cases against the State Attorney General and white-collar criminal defense matters. 

Brian C. Mahoney advises clients on matters related to corporate compliance and government investigations as well as federal and New York state regulatory actions. He handles NCAA matters including compliance and student athlete eligibility issues. He represents individuals, businesses and institutions in both civil and white-collar criminal matters. Brian has tried more than 80 civil and criminal jury trials to verdict. Prior to entering private practice, Brian served as the chief of the Felony Trial Bureau for the Erie County District Attorney, the largest upstate prosecutor’s office north of Westchester County. 

Joan P. Sullivan represents and advises businesses, individuals, and not-for-profits in a variety of federal and state criminal and civil litigation matters, regulatory proceedings, government investigations and corporate internal investigations, with particular emphasis on defending clients against claims of fraud. She represents executives and corporations in a wide range of industries, including healthcare, retail, construction, energy, IT, and higher education. Joan also counsels clients on compliance issues, focusing on government ethics, lobbying compliance, and government procurement processes. Joan has previously served as a counsel to the New York State Commission on Public Integrity, now known as the Commission on Ethics and Lobbying in Government. 

Christian R. Flemming’s practice focuses on corporate compliance, government ethics, lobbying compliance, and white-collar crime. He regularly advises individuals and corporations on compliance with federal, state, and local laws concerning government ethics and lobbying. Christian represents individuals, businesses and institutions in complex civil litigation, government administrative investigations, cases against the State Attorney General, and white-collar criminal defense matters. He has been engaged by Fortune 500 companies and other leading companies in the financial, health care, retail, environmental, transportation, and energy sectors to conduct sensitive regulatory and criminal investigations on national and state levels. 

About Lippes Mathias LLP 
Lippes Mathias is a full-service law firm with more than 135 attorneys serving clients regionally, nationally, and internationally. With offices in Buffalo, Albany, Rochester, Long Island, and New York, N.Y.; Greater Toronto Area; Chicago, Ill.; Jacksonville, Fla.; San Antonio, T.X.; and Washington, D.C., the firm represents publicly and privately-owned companies, private equity and venture capital firms, real estate developers, financial institutions, municipalities, governmental entities, and individuals. 

Year after year, Lippes Mathias is proud to be recognized by The Best Lawyers in America®, U.S. News - Best Lawyers®, Super Lawyers and Chambers USA. 
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