About Mark J. O'Brien

Mark J. O’Brien, Esquire is a nationally recognized Federal Criminal Defense Attorney with over 25 years’ experience in criminal courts all throughout the country. After beginning his professional career as a Miami, Florida prosecutor in the late 1990’s, Mr. O’Brien organized his own law firm in 2002 based upon the professional lessons he learned to that point in his life with the goal defending those accused of federal crimes with a mix of old school values and new school ideas.During first decade in private practice from 2002 to 2012, Mr. O’Brien defended individuals and corporations charged with federal crimes throughout federal criminal courts in Florida. From 2012 to the present, Mr. O’Brien has accepted the defense of clients in federal criminal courts throughout the entire country, in addition to his previously established practice in all federal courts in Florida. Case after case, success after success, in federal court after federal court, all throughout the country, has resulted in a growing legacy. To put it simply, Mr. O’Brien wins and, as a result, he is a lawyer in demand.Mr. O’Brien grew up in New York, attended law school near Philadelphia, Pennsylvania, and started his career in Miami, Florida. There is nothing he has not seen, done, or dealt with in and/or out of a criminal courtroom. New York raised, Philly tough, and Miami tested, Mr. O’Brien brings his 25 years of federal criminal court experience to those accused of federal crimes in federal criminal courts throughout the nation. Mr. O’Brien has the resources, both in his team and in his experience and his training, to tackle your federal criminal case and accomplish the only objective that matters: Win.A Federal Criminal Defense Attorney With a Federal Criminal Defense TeamIn addition to his experience and training, Mr. O’Brien has built a full Federal Criminal Defense Team to assist him in defending his clients. Mr. O'Brien believes in hiring the best people to help him do his job. Similar to his role as a former prosecutor, Mr. O’Brien hired people who used to work in various federal law enforcement capacities. It is important to stay one step ahead of the other side. The only true way to accomplish this goal is to have done what the other side is going to do.As a result, Mr. O'Brien supplements his experience and training with others who have very specific sets of skills. This includes a former Drug Enforcement Agency (DEA) Federal Special Agent, a former Internal Revenue Service (IRS) Criminal Investigation Division Federal Special Agent, a former United States Probation Officer, and a former law enforcement detective. Together, these four individuals have over 100 plus (over 25 years each) combined years’ experience in federal and state criminal courts throughout the country.Once the above individuals are added to his 25 years of prosecutorial and federal criminal defense experience, Mr. O'Brien's team has well over a 125 combined years of federal and state criminal court experience to help you through this precarious time in your life.Federal Criminal DefenseThe United States Constitution guarantees every individual the right to a fair trial and the presumption of innocence until proven guilty. This fundamental principle is upheld in federal criminal defense, where Mr. O’Brien works tirelessly to protect the rights of the accused.The role of a federal criminal defense attorney is to provide legal representation to individuals charged with federal crimes. These crimes can range from drug trafficking and white-collar crimes to terrorism and espionage. The stakes are high, as a conviction can result in lengthy prison sentences, hefty fines, and a criminal record that can follow an individual for the rest of his or her life.One of the key arguments in favor of hiring Mr. O’Brien for your federal criminal defense is the importance of protecting the rights of the accused. The Constitution guarantees the right to a fair trial, which includes the right to legal representation. Without a skilled attorney like Mr. O’Brien, a federal defendant may not fully understand their rights or the legal process, which can lead to an unfair trial and an unfair result.Another argument in favor of hiring Mr. O’Brien is the need to ensure that the government follows due process. The government has vast resources at its disposal, including federal and state law enforcement agencies and prosecutors. A skilled defense attorney like Mr. O’Brien will level the playing field by challenging the government's evidence and ensuring that you are treated fairly.White collar crime is a term used to describe non-violent crimes committed by individuals in positions of power or trust, typically in the business or financial sectors. These crimes can include fraud, embezzlement, insider trading, and money laundering, among others. When accused of such crimes, individuals often seek the white collar criminal defense services of Mr. O’Brien to represent them in federal criminal court.Mr. O’Brien’s role is to protect the rights of his clients and ensure they receive a fair trial. This can involve challenging the evidence presented by the prosecution, negotiating plea deals, and presenting a strong defense case. In many cases, wherein trial is not the best option, Mr. O’Brien will work to mitigate the potential consequences of a conviction, such as fines, restitution, and most importantly imprisonment.One of the key arguments in favor of retaining Mr. O’Brien is that everyone is entitled to a fair trial, regardless of the nature of the crime they are accused of committing. This is a fundamental principle of the American justice system, and it is the responsibility of the defense attorney to ensure that this principle is upheld. Additionally, Mr. O’Brien can help to prevent wrongful convictions by challenging the evidence presented by the prosecution and presenting a strong defense case with his federal criminal defense team.Federal criminal defense attorney Mark J. O’Brien is a crucial component of the American justice system. He ensures that the rights of the accused are protected, and that the government follows due process. While the stakes are high, a skilled federal criminal defense attorney like Mr. O’Brien can make a significant difference in the outcome of a federal case. Why play games with your life?Mr. O’Brien handles all federal criminal court areas of practice, including but not limited to: Federal White Collar Criminal Defense, Federal Sex Crimes Defense, Drug Crimes, Gun Crimes, Conspiracy Crimes, General Federal Criminal Defense, Federal Grand Jury Investigations and Pre-File Criminal Investigations.Mr. O’Brien has been a member of the Bar of the State of Florida and the Bar of the Commonwealth of Massachusetts since 1998. He has been a member of the Bar of the State of Montana since 2023. In addition, he is a member of the Supreme Court of the United States, the Supreme Court of the State of Florida, the Massachusetts Supreme Judicial Court, the Montana Supreme Court, and he has appeared as a member or a pro hac vice member before many federal district courts.If you are being investigated and/or prosecuted by federal agents and/or federal prosecutors and are need of a Federal Criminal Defense Attorney – and a Federal Criminal Defense Team – anywhere in the United States of America, all Mr. O’Brien needs is a Wi-Fi Password and a plane to defend you.

 

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Criminal Law
Posted by Alfred
June 13, 2024
Hired Attorney

I would trust this particular lawyer and his firm with my life they gave me a great outcome never lied to me told me what was to be expected and always kept me informed. I worked with AC Jeanette as well as attorney Mark O'Brien the outcome was phenomenal.

Federal Criminal Law
Posted by Monica
June 06, 2024
Hired Attorney

I don’t even know where to begin with this review. When I met Mr. Obrien in 2010 I had violated my Federal probation. I didn’t know how it was going to end I was 6 months pregnant and luckily there were no more public defenders so the judge assigned Mr. Obrien as my public defender. Mr. O’brien did above and beyond the call of his duties. When I went to court for my state case they told me that I had retained private council. I was quite shocked. Unbeknownst to me, Mr. O’brien had taken on my state case pro bono as a part of my defense and his kindness. He fought me as if his life depended on it. I walked away reinstated. Mr. O’brien and his team is so awesome they’re kind, caring and concerned about their clients needs. His assistant Jeanette, you can call her anytime of night or day and she’ll comfort you to assure you that Mr. O’brien has your best interest. In 2022 I got another case a little different but again he stepped right in.

 
White Collar Crime
Posted by anonymous
June 05, 2024
Hired Attorney

You come to a lawyer scared and likely confused about what's going to happen next. How serious is this accusation and is there the possibility of being exonerated? Mark did an amazing job of calming our fears with facts and details and a plan of action. He was very honest about the areas of "concern" and the things he could do to paint things in a favorable light. He then thoroughly defended and protected us. He investigated the rules, identified the gray areas, and showed how we didn't have any intent to break them. He then came up with a plan of action to get the charges dropped with a way to maintain good favor with the authority in question. No one wants to be in this situation but Mark (and his ENTIRE staff) made it the most tolerable experience possible and eventually ensured the absolute best outcome imaginable.

 

Services

Areas of Law

  • Appellate Practice
  • Criminal Law 3
    • Federal Criminal Law
    • Drug Crimes
    • Weapons Charges
  • White Collar Crime
  • Personal Injury 1
    • Sexual Abuse
  • Assault
  • Labor and Employment 1
    • Whistleblower Litigation
  • RICO
  • Qui Tam Litigation
  • Securities 1
    • Securities Fraud
  • Consumer Law 1
    • Identity Theft
  • Other 43
    • Criminal
    • Criminal Appellate
    • Litigation/Trial Advocacy/Advocacy
    • Appeals and Post-Conviction Motions
    • Money Laundering
    • Embezzlement
    • Bribery Crimes
    • Foreign Corrupt Practices Act
    • Antitrust Violations
    • Public Corruption
    • Racketeering
    • Hydrocodone/Vicodin
    • Oxycodone/OxyContin Possession and Distribution
    • Drug Selling or Trafficking
    • Tax Evasion
    • Murder
    • Extradition
    • Healthcare Fraud
    • Pornography
    • Indecent Exposure
    • Drug Possession
    • Drug Distribution
    • Drug Manufacturing
    • Internet Crime
    • Sexual Battery
    • Enticement
    • Environmental Violations
    • Fair Claims Act
    • Child Pornography
    • Tax Fraud
    • Mail Fraud
    • Wire Fraud
    • Mortgage Fraud
    • Medicare Fraud
    • IRS Issues
    • Insider Trading
    • Ponzi Schemes
    • Sarbanes Oxley
    • Conspiracy to Commit a Federal White Collar Crime
    • All Other Federal White Collar Crimes
    • Gun Offenses
    • All Other Federal Crimes
    • Federal Grand Jury Investigations

Practice Details

  • Languages
    Spanish
    English
  • Payment Information
    Payment & Cost Features
    Free initial consultation
    Fixed fees available
    Accepted Credit Cards
    American Express
    Discover
    MasterCard
    Other
    Visa
  • Firm Information
    Position
    Founder
    Firm Name
    O'Brien Hatfield, PA
  • Pro Bono Services

    We do not offer pro bono (or free) legal fees. or services.

  • Additional Links

Experience

  • Bar Admission & Memberships
    Admissions
    1998, Florida
    1998, Massachusetts
    U.S. District Court
    U.S. District Court, Western District of Tennessee
    U.S. Court of Appeals for the Eleventh Circuit
    U.S. District Court, Northern District of Florida
    U.S. Supreme Court
    U.S. District Court, Middle District of Florida
    U.S. District Court, Nor
    U.S. Court of Appeals for the First Circuit
    U.S. District Court, Southern District of Florida
    2023, Montana
    United States District Court for the District of Massachusetts
    United States District Court for the District of Montana
    United States District Court for the Eastern District of Texas
    United States District Court for the District of North Dakota
    United States District Court for the Southern District of Indiana
    United States District Court for the Northern District of Texas
    United States District Court for the Western District of Texas
  • Education & Certifications
    Other Education
    Siena College
    Class of 1995
    B.A.

    Widener University School of Law
    Class of 1998
    J.D.

Contact Mark J. O'Brien

Founder at O'Brien Hatfield, PA
4.9
60 reviews

511 W Bay St.Suite 330Tampa, FL 33606U.S.A.

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1001 Brickell Bay Drive Suite 2700 M-1Miami, FL 33131U.S.A.

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121 South Orange Avenue, Suite 1500Orlando, FL 32801U.S.A.

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Other Office Locations

Miami, FL

1001 Brickell Bay Drive Suite 2700 M-1Miami, FL 33131U.S.A.

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Orlando, FL

121 South Orange Avenue, Suite 1500Orlando, FL 32801U.S.A.

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Attorneys FAQs

  • What year was this attorney first admitted to the bar?
    Mark J. O'Brien was admitted in 1998 to the State of Florida and Massachusetts.
  • Is this attorney admitted to the bar in more than one state?
    Yes, Mark J. O'Brien is admitted to practice in Florida, Massachusetts and Montana.
  • Is this attorney admitted to practice in any U.S. Federal Courts?
    Mark J. O'Brien is admitted to practice before the United States Court of Appeals for the Eleventh Circuit, United States Court of Appeals for the First Circuit, United States District Court for the District of Massachusetts, United States District Court for the District of Montana, United States District Court for the District of North Dakota, United States District Court for the Eastern District of Texas, United States District Court for the Middle District of Florida, United States District Court for the Northern District of Florida, United States District Court for the Northern District of Texas, United States District Court for the Southern District of Florida, United States District Court for the Southern District of Indiana, United States District Court for the Western District of Tennessee, United States District Court for the Western District of Texas and United States Supreme Court.
  • Does this attorney speak any other languages?
    Mark J. O'Brien speaks Spanish.