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"Lawyer of the Year"

Harris County Criminal Lawyers Association (2014)

Houston DWI Attorneys

Experienced DWI Attorneys in Houston, TX

Houston DWI Attorney Casey Keirnan

Criminal defense attorneys John P. Keirnan and Michael Mercer have a proven track record of success defending DWI charges in Houston and Harris County, Texas. For more than 40 years, the experienced DWI attorneys at Mercer & Keirnan have fought hard for Texans charged with DWI, taking many cases to trial.


Your best possible chance of successfully fighting a DWI charge in Houston is to work with an experienced DWI attorney who knows how to defend your rights. Call us now for a free consultation and speak with a top Houston criminal defense attorney about your DWI case.

Facing DWI /DUI charges in Houston? Contact us at (713) 236-9700 today for a free consultation.

Experienced Houston DWI Attorney
  • Over 40 years of experience defending DWI charges in Houston

  • Awarded "Lawyer of the Year" and "Lifetime Achievement Award" from the Harris County Criminal Lawyers Association

  • Recognized in the news as a top Houston DWI attorney

  • We give clients our personal cell phone numbers for direct communication

  • 5 star rating on Google

  • The vast majority of our cases result in dismissal

  • Free 24/7 consultations for your DWI charge

DWI Defense Attorneys Casey Keirnan and Michael Mercer have experience defending the following specific DWI and alcohol related charges in Houston:

Penalties for DWI Charges in Texas

DWI 1st Offense (Class B Misdemeanor)

Texas Penal Code Sect. 49.04

  • Confinement in county jail for a minimum of 6 days and maximum of 180 days and/or a fine of up to $2,000

  • Drivers license suspension of 90 days for anyone who takes a time-served plea, as opposed to a probation

  • Additional Conditions – depending on the facts of your case (accident, prior record, alcohol problem, etc.), the court may order additional conditions, such as an Ignition Interlock Device, Alcohol Treatment, random drug tests, pr restitution.

DWI 2nd Offense (Class A Misdemeanor)

Texas Penal Code Sect. 49.04

  • Ignition Interlock Device – required as a condition of bond in a DWI 2nd Offense, as well as a condition of probation after a guilty plea. The Ignition Interlock device requires a breath sample before starting your car and periodically while driving.

  • Confinement in county jail for not less than 72 hours nor more than one year and/or a fine of up to $4,000

  • Drivers license Suspension for not less than 180 days nor more than two (2) years, if convicted


Call the Houston DWI attorneys at Mercer & Keirnan to find out how to avoid getting your license suspended or to apply for an occupational license.

DWI 3rd Offense or Greater (3rd degree felony)

  • Ignition Interlock Device – required as a condition of bond while your case is pending as well as a condition of any occupational or provisional licenses after conviction.

  • Confinement in prison for between 2 to 10 years and/or a fine of up to $10,000 

  • Drivers license suspension of up to 2 years beginning after your release from confinement

  • Other – mandatory rehabilitative treatment for alcohol/drugs

Intoxication Assault DWI (3rd degree felony)

A person commits intoxication assault DWI if by accident or mistake, while operating a motor vehicle in a public place while intoxicated, a person by reason of that intoxication causes serious bodily injury to another. ‘Serious bodily injury’ means injury that creates a substantial risk of death or protrated loss or impairment of the function of any bodily member or organ.

  • Fine – not to exceed $10,000.

  • Jail – confinement in prison for a term of not less than two (2) years nor more than (10) years.

Intoxication Manslaughter DWI (2nd degree felony)

A person commits intoxication manslaughter DWI if, while operating a motor vehicle in a public place, an intoxicated person, by reason of that intoxication, causes the death of another by accident or mistake.

  • Fine – not to exceed $10,000

  • Jail – confinement in prison for a term of not less than two (2) years nor more than twenty (20) years

The Houston DWI attorneys at Mercer & Keirnan are ready to fight hard for you. With more than 40 years of combined experience in DWI defense, our DWI attorneys can show you the best course of action to take. Contact us at (713) 236-9700 to talk to a DWI attorney for a free evaluation of your case.

Client Reviews


Perfect 5 Star Google Rating


Mr Mercer is really good at what he does. I would recommend Mr Mercer to anyone that needs a good lawyer. he's on top of everything keeps you informed and works hard on your case. I'm extremely grateful for him working so diligently on my case. I appreciate how he took the time to look at all the paperwork that I had given him and to get to know a little bit about me. I'm definitely confident with giving him a five-star rating.

by R. C. 5/8/2024 on Google


"Michael Mercer and Casey Keirnan are some of the best criminal defense attorneys in Houston. I was facing an aggravated assault with a deadly weapon charge in Harris County and they got this felony assault case dismissed outright with no probation. Anyone charged with assault or aggravated assault in Houston should strongly consider calling Mercer and Keirnan Criminal Defense Attorneys. I couldn’t be happier with how they handled my case!"

by H. I. March 8, 2024


"I hired Mercer and Keirnan because of their experience handling DWIs and other charges.  Working closely with them throughout my case, it became very clear that I had made the right decision..."

by T. M. December 30, 2018


"Never been in trouble before and now I couldn't bond out of jail and had a court appointed lawyer who gave me little hope. I found defense attorney Casey Keirnan and Michael Mercer because of their experience as a theft defense lawyer. They replaced my court appointed attorney and everything changed."

by D. O. August 27, 2018


"I hired a top Houston drug lawyer with Mercer and Keirnan to defend my possession of a Controlled Substance Case. After a free consultation with Criminal defense attorney Michael Mercer, Mercer and Keirnan signed on to my case and after a few months my felony drug charge was dismissed!"

by RG One February 5, 2019

DWI Attorney for Driver's License Suspensions

Depending on the facts of your DWI case, you will likely need to hire a DWI Attorney to contest the suspension of your Texas Drivers License. Texas law imposes an automatic suspension of your license if you refused to the taking of a breath specimen or if your blood alcohol content was over .08. Your DWI attorney can contest this suspension by requesting a hearing. The hearing must be requested within 15 days of your arrest, so don't waste time in hiring a top DWI lawyer to defend you.

Call 713-236-9700 for a free evaluation, or Request a Quote Online

Top Houston DWI Attorney available 24/7

License Suspension Periods in DWI Cases


  • Refused breath test– not less than 180 days.

  • Provided breath test– not less than 90 days IF you blew over .08 BAC.


  • Refused test – not less than 180 days.

  • Provided test – not less than 60 days IF any alcohol detected.

Contact a Houston DWI attorney at Mercer & Keirnan NOW to learn how to prevent your license from being suspended. Time is of the essence.

Hire an Experienced Houston DWI Lawyer

The punishment in each DWI case will differ based on the facts and also on the DWI Defense Lawyer you hire. After over 40 years of experience as a Houston DWI Lawyer, Casey Keirnan understands the pretrial and trial processes in DWI cases like few other attorneys in the area.


An experienced Houston DWI Lawyer knows how to beat a DWI case, either through the selective pretrial intervention programby setting the case for trial, by filing motions to suppress illegally obtained evidence or by winning based on problems with the breath and blood tests. Clients who hire defense attorney Casey Keirnan have high expectations when it comes to defending their DWI's and negotiating for the best possible result in each case.

dwi defense lawyer

DWI Cost in Texas

The cost of a DWI in Texas can be extremely burdensome. There are attorneys' fees, bail bonds, court fees, DPS fees, probation fees, ignition interlock fees and more. Next to spending time in jail, the cost of a DWI on the person accused might be the most daunting aspect of a DWI charge. Depending on the DWI lawyer you hire and whether you get convicted, a DWI could cost you up to $30,000 when all is said and done.

Factors that Affect the Cost of a DWI

  • Attorney fees: anywhere from $3,000 to $20,000. As with all other industries, you get what you pay for when it comes to a DWI Lawyer. Do your research on whomever you hire. Meet with the lawyer in person before retaining them.

  • Bail bond fees: most misdemeanor DWIs will qualify for a PR bond, which costs you nothing. Felony DWIs may come with bonds between $5,000 and $30,000, depending on the facts of the case.

  • DPS Superfine fees: should you get convicted of a DWI in Texas, DPS assesses fees between $3,000 and $6,000. Have your DWI lawyer request the judge to waive these fees during your plea.

  • Probation fees: standard probation fees in Harris County, TX are around $70/month. This does not include any fine you agreed to pay as part of your probation. This also does not include the cost of installing and maintaining an interlock device in your vehicle should the judge require one

Can I Get a DWI Off of My Record in Texas?

Depending on the outcome of your DWI case, you may be eligible to get a DWI off of your record by filing for either a Non-Disclosure or an expunction. In Texas, expunction of DWI arrests are only available in the following situations:

  • your DWI case resulted in a dismissal

  • you received a Not Guilty verdict at trial and were acquitted

  • you successfully completed a pretrial diversion program

Expunction of a DWI case results in the destruction of any and all records arising from the arrest, no matter who created them. This is different from a Petition for Non-Disclosure, which allows for certain state agencies to maintain records of the arrest, even after the case has been sealed.

In order to get a DWI off of your record by way of a Non-Disclosure, you must meet one of the following conditions:

  • successful completion of a deferred adjudication

  • a guilty plea resulting in conviction, as long as you have no other criminal history and your blood alcohol level was under .15 (thanks to the newly enacted Non-Disclosure laws in 2017)

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