Legal services for Colorado's Front Range

Kellen Law Firm

Aggressive Legal Defense for the Front Range


Trial Attorney - Former Prosecutor

If you are being prosecuted, who better to have on your team than an attorney who is intimately familiar with how the District Attorney’s office thinks?

Kellen Law Firm provides legal services along Colorado's Front Range. Our focus is Criminal Defense, including DUI and traffic. Attorney William Kellen is a former felony criminal prosecutor who began his career prosecuting in Chicago, and has years of experience handling thousands of criminal cases and dozens of jury trials. Whatever your legal problem, we can plan the best response, whether that means negotiating a plea bargain or preparing for a trial.

Mr. Kellen has extensive experience in DUI cases involving both alcohol and marijuana. He has attended numerous law enforcement trainings on how roadside sobriety testing and chemical testing is conducted, and is very experienced in ways to challenge those tests.

Kellen Law Firm only represents individuals and small businesses, and Mr. Kellen personally handles every case. Initial consultations are free, and we have flat-rate pricing available for most cases. Please call or e-mail today to schedule a consultation.

Attorney William Kellen

Attorney William Kellen

(720) 446-9698




Criminal defense

Felonies, misdemeanors, or petty offenses in County, District, Municipal, or Federal Court, from the initial filing of charges through the trial. Mr. Kellen is experienced in suppressing evidence, asserting defenses, and negotiating with prosecutors. We will fight for the best plea bargain, or plan to fight the case at trial. Services offered include consultation when an individual is contacted by a police officer who asks to speak with them about an open investigation. Know your rights before you make a statement!

Underage Alcohol or Marijuana

These charges can impact education and employment opportunities. We can help ensure that this doesn't throw you or your family member's life off track.

DUI Defense

Whether it's a first offense or a Felony DUI, we can explain your rights and options. Mr. Kellen has conducted numerous jury trials involving a variety of DUI issues, and is familiar with roadside testing, chemical testing, refusal of testing, and cases that focus on physical control of a vehicle rather than actual driving. It is important to understand the possible penalties you are facing based on your personal background, and the defenses available based on the evidence in your case. Services offered include representation at a DMV Hearing, motions practice, and jury trial.

Traffic Violations

Careless driving, reckless driving, leaving the scene, and speeding 20+ mph over the limit can cause serious problems. Mr. Kellen has handled many cases involving these charges, including cases with serious injury and fatality. Find out how to keep or reinstate your driver's license. Services offered include plea negotiations with the prosecutor to seek dismissal or reduce points.

juvenile court

The rules are different in Juvenile Court, and sometimes the court system needs to be reminded that there is a child involved. We can explain the difference between a conviction and an adjudication, and why the court system appoints a separate attorney called a GAL. We will make sure your family navigates this process as smoothly as possible.


Mr. Kellen has personally handled cases filed in the Courts of the following Colorado Counties:

  • Denver

  • Jefferson

  • Arapahoe

  • Adams

  • Douglas

  • Broomfield

  • Boulder

  • Larimer

  • El Paso

  • Pueblo

  • Teller

  • Summit

  • Garfield

  • Otero

  • Crowley


He who represents himself has a fool for a client.
— Attributed to Abraham Lincoln