John T. Mulcahy

/My focus

I am a trial attorney with substantial federal criminal defense, white-collar, tax, and general litigation experience. I defend individuals and businesses in complex tax, fraud, and public corruption matters, as well as civil enforcement cases. I have extensive trial experience involving healthcare fraud, corporate and employment tax fraud, FDA violations, FinCEN violations, and COVID-19-related fraud.

My practice includes the following areas:

Federal Tax Enforcement

I have extensive experience in tax enforcement matters. I worked at the DOJ Tax Division for more than four years and handled numerous tax matters in my eight years at the US Attorney’s Office, including multiple trials involving tax charges. My previous tax law matters have included tax evasion, tax obstruction of justice, employment tax, and false tax returns. I have also gained experience related to enforcement of the trust fund penalty, as well as IRS collection and audit procedures, and IRS civil procedures more generally. I have gained special recognition two times from the Tax Deputy Attorney General for outstanding trial work on tax cases.

Trials and Civil Litigation

I am equipped to successfully lead and assist on civil and criminal trial teams. I have tried 11 cases in federal court and more than 30 in state court. I have appeared before virtually every federal judge in the District of Massachusetts. My experience includes jury trials, motion hearings, plea hearings, and sentencing hearings. My trial experience includes expert witness direct- and cross-examinations, and cross-examination of defense witnesses. I have handled civil matters in both state and federal courts in Massachusetts, Rhode Island, Illinois, Indiana, Nevada, and Kansas.

White-Collar Defense

I have extensive white-collar experience in a variety of different matters. My public corruption defense practice has focused on high-profile public figures in Massachusetts, such as a former state senator, Boston city council member, and county sheriff. I brought two healthcare fraud cases to trial against doctors and other medical professionals, resulting in convictions. I also tried a case involving cryptocurrencies and federal anti-money laundering regulations. I am experienced in litigating cases involving the major white-collar statutes, including wire fraud, smuggling, extortion, conspiracy, and bank fraud. In addition, my experience includes representing clients in investigations involving multiple witnesses needing representation and/or targets, both in state and federal courts, as well as counseling clients who are served with grand jury subpoenas for financial and business records.

/Representative experience

Federal TAX Enforcement Defense

• Twelve years handling federal tax prosecutions at the US Attorney’s Office and DOJ Tax Division, including complex cases involving trust fund recovery penalty, employment taxes, affirmative acts of evasion, and loss-carryback defense
• Experienced with identity theft, false claims, and theft of government funds charges as part of federal tax prosecutions
• Represented tax professionals in federal criminal tax investigation involving offshore tax shelters and unreported foreign income

Federal and State Trial

• Tried 11 federal jury trials and more than 30 state jury trials involving public corruption, tax, healthcare, cryptocurrency and digital asset regulations, money laundering, and narcotics
• Experienced with all phases of trial litigation, including motions in limine, jury instructions, and jury questionnaires
• Experienced with witnesses of various backgrounds, including victims, expert witnesses, cooperating witnesses, law enforcement witnesses, and records custodian witnesses

Healthcare Fraud

• Tried federal jury trials in the District of Massachusetts against medical doctors resulting in convictions, including matters involving Medicare and Medicaid upcoding and impossible day billing schemes
• Experienced in matters involving HHS and FDA laws and regulations, labeling requirements, and the new drug application process
• Experienced in financial matters involving medical professionals, including alleged money laundering and management of business versus personal income and expenditures

White-Collar Defense

• Conducted internal investigation for a nonprofit organization involving suspected embezzlement and financial fraud by a senior corporate officer
• Represented client in federal grand jury investigation involving money laundering and financial crimes
• Counseled business client in federal export control investigation involving potential OFAC and Export Administration Regulations violations

/Looking ahead

I expect that the federal government will continue vigorously investigating and prosecuting tax matters and healthcare fraud. Given administrative priorities, there likely will be more attention by federal authorities on immigration and national security aspects of investigations. I also expect the federal government to increase its enforcement of COVID-19-related fraud, including fraud related to the Employment Retention Credit (ERC), the Payroll Protection Program (PPP), the Pandemic Unemployment Assistance Program (PUA), and the Economic Injury Disaster Loan Program. As to tax enforcement matters, the government will continue pursuing investigations of offshore tax shelter schemes, tax promotion schemes, and high net-worth individuals. Given these current trends, it is essential that individual and corporate clients understand their compliance and ethical responsibilities, and have sound, competent, and vigorous defense representation when they face a federal investigation or prosecution.

/Prior Government Experience

ASSISTANT US ATTORNEY FOR THE DISTRICT OF MASSACHUSETTS, 2018–2026

• Prosecuted a wide variety of federal criminal cases, including public corruption, tax fraud, healthcare fraud, FDCA violations, wire fraud, bank fraud, cybercrimes, money laundering, firearms charges, perjury, false statements, and smuggling
• Prosecuted numerous criminal tax cases, including an employment tax fraud matter involving more than $20 million in unreported payroll, tax evasion, false tax return, and identity theft
• Secured a guilty verdict in a 2024 jury trial against a psychiatrist who sold non-FDA-approved prescription drugs and laundered funds to Hong Kong to purchase drugs
• Secured guilty verdict in 2024 jury trial against former Massachusetts state senator for wire fraud and tax fraud related to pandemic unemployment benefits and unreported income
• Secured guilty verdict in 2024 jury trial against a cryptocurrency exchanger for money laundering and operating an illegal money services business
• Secured guilty verdict in 2023 jury trial against psychiatrist who prescribed Schedule II and IV controlled substances outside standard of care
• Tried four other cases to verdict and managed all phases of litigation, including grand jury practice, immunity orders, complaints, indictments, plea agreements, motions to dismiss, motions to suppress, and sentencing memoranda
• Successfully prosecuted registered nurse for tampering with consumer product and fraud
• Co-led working group in Boston and Worcester offices with other federal prosecutors, partnering with law enforcement agents from numerous federal, state, and local law enforcement agencies to develop investigations and prosecutions from reports regarding allegations of fraud and money laundering

UNITED STATES DEPARTMENT OF JUSTICE, TRIAL ATTORNEY, TAX DIVISION, WESTERN CRIMINAL ENFORCEMENT SECTION (2014–2018)

• Directed approximately 25 criminal tax matters, including drafting indictments, motion practice, plea negotiations, and sentencing, in federal district courts in Illinois, Indiana, Montana, Nevada, and Kansas
• Reviewed and authorized tax prosecutions, including high-profile matters involving a former celebrity and law enforcement officer in California and a former Chicago alderman/attorney
• Secured guilty verdict in jury trial against a business owner who used identities from death registry to file millions of dollars in fraudulent tax claims
• Secured guilty verdict in jury trial against home healthcare business involving trust fund recovery penalty and tax fraud of more than two million dollars in the District of Nevada
• Secured guilty verdict in jury trial against registered nurse-owner of med spa who committed personal and corporate tax evasion involving millions of dollars of cash receipts

MIDDLESEX DISTRICT ATTORNEY’S OFFICE, ASSISTANT DISTRICT ATTORNEY, APPEALS AND DISTRICT COURT UNITS (2012–2014)

• Conducted approximately 30 jury trials
• Briefed and argued approximately 10 appeals before the Massachusetts Supreme Judicial Court and Appeals Court
• Second-chaired murder and elder fraud trials

/Clerkship

• Honorable Edward F. Harrington of the US District Court in Boston (2008–2010)

/Insights

• “Federal Criminal Tax Enforcement: From Investigation to Trial and What’s Next,” Boston Bar Association Webinar, June 2026
• “Record of Consultation: Criminal Tax Enforcement,” (Im)material Podcast, John Mulcahy and Jonathan Schnatz, June 2026
• “Marinello After Eight Years: The Nexus Requirement and the Modern 7212(a) Tax Obstruction Case,” with Samuel J. Ryder, Practising Law Institute, June 2026
• “Potential COVID-19-era tax refunds—Act before July 10, 2026,” Nixon Peabody Alert, June 2026
• Speaker, “Investigation and Prosecution of Psychiatrist for Illegal Distribution of Drugs and Healthcare Fraud,” Northeast Healthcare Law Enforcement Association Training, May 2026
• “Inside a Criminal Tax Case,” Tax Rep Network Podcast, May 2026
• “DOJ Escalates Civil Denaturalization Enforcement,” Nixon Peabody Alert, May 2026