Legal services for Colorado's Front Range

Attorney Bio




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(720) 446-9698



William D. Kellen, Esq.

Mr. Kellen is a Colorado native who graduated from Colorado State University before moving to Chicago to attend DePaul University College of Law. After graduation, he worked as a criminal prosecutor for the City of Chicago, practicing in Cook County Circuit Court. He was directly involved in the litigation that resulted from the United States Supreme Court's ruling in McDonald v. City of Chicago, 561 U.S. 742 (2010).

In 2011, William moved back to Colorado and subsequently worked for several years as a Deputy District Attorney at the 4th Judicial District Attorney's Office in Colorado Springs. In that office, he was the lead prosecutor on hundreds of felony cases, including cases involving domestic violence, drugs, guns, assault, kidnapping, arson, aggravated robbery, burglary, serious bodily injury, and homicide.

In his years as a prosecutor and criminal defense attorney, Mr. Kellen has personally handled thousands of cases and conducted dozens of jury trials. He has received extensive training in how law enforcement investigates and prosecutes DUI cases, including roadside testing and chemical testing. He has also represented hundreds of individuals in civil practice (negligence and breach of contract claims), personally recovering millions of dollars for his clients. This varied experience gives William a unique understanding of how civil claims overlap with the criminal justice system.

Mr. Kellen has been in private practice since 2016, and opened the Kellen Law Firm in order to assist those accused by our criminal justice system. His significant trial experience, combined with his experience as a former prosecutor, give him tremendous insights into the best plan of advocacy.



DePaul University College of Law
Juris Doctor

Colorado State University
B.S., Business Administration


• Colorado Criminal Defense Bar, Member
• Colorado Trial Lawyers Association, Member
• Colorado Bar Association, Member

Bar Admissions

• Colorado
• Illinois
• United States District Court for the District of Colorado