Proven Criminal Defense Attorneys

Last updated on March 31, 2026

Mark J. O’Brien, is a leading criminal defense firm based in Tampa and serving clients in Orlando and across Florida and beyond. Our law firm concentrates on defending people facing the most serious criminal allegations. Over our firm’s history, our lawyers have achieved favorable results for clients facing a variety of charges.

Determined Advocates For People Facing White Collar And Other Criminal Charges In Florida

Our law firm defends individuals facing the full range of white collar criminal accusations in state and federal courts across Florida, including St. Petersburg, Hillsborough County and Lakeland. In addition, we protect clients facing drug charges and accusations of sex offenses. Our law firm will aggressively defend you against these allegations in the courthouse and in the court of public opinion. We are dynamic, discreet professionals who will closely examine the facts of your case and determine the best possible strategy.

Practice Areas

Our law firm handles all types of state and federal criminal cases, mounting a strong defense for every client. Examples of our cases include:

• Assault and aggravated assault
• Battery and aggravated battery
• DUI
• Gun cases
• Misdemeanors
• Theft cases
• State crimes and state sentencing issues

Our Florida law firm also defends people against other serious federal charges, including health care fraud, transporting illegal aliens and child and possession of a firearm by a felon. We understand that the government often has significant leverage in these prosecutions. We have a history of achieving successful outcomes in the face of seemingly insurmountable odds. To learn more about the differences between prosecutions at the state and federal levels, please see our guide to federal criminal court.

Our 10-Point Promise

People facing criminal charges usually have no experience with such matters and have only the vaguest idea of what to expect. To help our clients, we have developed a “10-Point Promise” that spells out how we will handle your case”

1. We do not guarantee a federal or state case result. Any lawyer or law firm that does is not being honest. The results we discuss are 100 percent the results of attorney Mark J. O’Brien, real, accurate and fully supported by federal court documents but they are past results. No one is able to predict the future. However, based upon our experience and our training we believe it is possible to alter a case based upon the facts and the law we are presented with in a legal case.
2. We will provide you with an initial written sentencing analysis immediately upon hiring our law firm. This sentencing analysis will explain all of the penalties associated with state crimes, the United States Sentencing Guidelines and the Statutory Mandatory Minimums that may come into play if you are found guilty at trial or if you plead guilty and forego a trial. We employ a former United States probation officer of 26 years to assist us in this effort. You will know what we know, and you will know it immediately.
3. We will provide you with a full written analysis of your presentence investigation report (PSI), if there is one, and if it is different from what we predicted in our initial sentencing analysis.
4. We will file a sentencing memorandum outlining all of our factual and legal objections to the presentence investigation report (PSI) along with a 3553(a) variance analysis detailing all mitigating factors at least one day prior to your sentencing where appropriate.
5. We provide mental health experts to assist in our defense where appropriate.
6. We provide private investigators to assist in our defense where appropriate.
7. We will keep you updated on your case through letters, status reports and conferences as much as possible. You will know what we know.
8. If you desire, we will keep your family and/or friends updated on your case through letters, status reports and conferences as much as you choose. They will know as much as you want them to know.
9. If you desire a trial, we will prepare and fight as aggressively as we can. Having first chaired 21 federal trial cases in federal criminal courts all throughout the country, we have the experience necessary to fight in trial — and also the experience of not only proceeding to federal trials, but also having won federal trials.
10. Post-sentencing we will review with you your appellate options and give you a written form to document your choice to pursue an appeal or not pursue an appeal.

Providing A Skilled, Aggressive Defense Against Drug Charges And Other Crimes

At O'Brien Hatfield, our Florida drug possession lawyers defend individuals facing all types of state and federal drug charges, including possession, distribution, manufacturing and conspiracy. We defend people accused of distributing, manufacturing or possessing any kind of illegal drug, from methamphetamine and cocaine to heroin and marijuana.

We have significant experience defending people against crimes related to selling or possessing oxycodone and other prescription drugs. Whatever crime you are alleged to have committed, our law firm will fully protect your rights and seek the best available result under the facts of your case.

Providing Strong Representation At All Stages Of The Criminal Justice Process

In addition to our work at the trial level, our firm represents clients in appeals and in post-conviction relief. If your trial was marred by procedural or substantive errors that led to an unfavorable outcome, our lawyers will make a strong case for relief before the appropriate court.

Florida Criminal Defense FAQs

If you have been arrested and charged with a criminal offense in Florida, it is important to understand your rights and the legal process. Here are some frequently asked questions and their answers to help guide you.

What steps should I take immediately after being charged with a crime?

Once official charges have been filed, contact an experienced criminal defense attorney right away to prevent worsening your situation. Avoid making any statements to law enforcement without your attorney present. Speaking with the police, even in a seemingly informal situation, can lead to accidental self-incrimination.

What are the differences between state and federal criminal charges?

State criminal charges are prosecuted at the state level and involve violations of state laws. For example, a theft or assault in the Tampa area will likely lead to state rather than federal charges.

Federal charges arise when federal laws are broken, such as drug trafficking or serious white collar offenses. These cases are handled in federal court and often pose complex legal procedures and carry harsher penalties. They are also subject to potentially unfavorable federal sentencing guidelines.

What are the potential outcomes of my criminal case?

It varies depending on the specific charges you face, their severity and any evidence against you. Of course, a conviction is possible, which can result in imprisonment for severe crimes.

Other possible outcomes include acquittal, dismissal of charges, plea bargain or probation. Additionally, alternative sentencing options like diversion programs may be available for some offenses. However, it may involve pleading guilty to the crime you are accused of committing.

What factors could influence the sentencing in my case?

Several different things can influence or play a role in the sentencing, such as:

• The severity of the offense
• The defendant’s criminal history
• Aggravating or mitigating circumstances

Other factors can include cooperation with law enforcement and the impact on victims, and any restitution paid. A skilled defense attorney can help present evidence and arguments to potentially reduce the sentence.

Contact O’Brien Hatfield

We offer a free initial consultation to discuss the specifics of your case. No matter where you are in Florida, we are ready to help. To get started, call en Español at 813-440-2347 or complete our contact form.

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