Our Attorneys

Birk Baumgartner

Birk Baumgartner

Managing Attorney

My name is Birk Baumgartner, and I am the principal at Baumgartner Law, LLC. I graduated Cum Laude from Southern Methodist University Dedman School of Law, and have been a litigator ever since.

I am the fourth attorney in my family, but unlike my family members, I declined a job at a big law firm. Instead, I decided to dedicate my practice to a limited number of cases, with focused and individualized care and the freedom to take only those cases that I believe are just.

I believe that access to great legal counsel should not be limited to those that can provide large up-front retainers. I will always listen to anyone’s legal questions and provide the best advice possible; and I will work to find a financial arrangement that works for you.

Sean Simeson

Sean Simeson

Civil Litigation Director

Sean Simeson is an Associate Attorney at Baumgartner Law. Previously, he worked in plaintiff personal injury and workers’ compensation firms where he represented individuals against large insurance companies in state and federal courts.

In addition to his personal injury experience, Sean represents people accused of criminal charges. He focuses on providing thorough and exhaustive representation to all clients from the intake through jury verdict.

In law school, Sean was the President of the Student Animal Legal Defense Fund; he was an assistant attorney for Southeast Louisiana Legal Services, and he received awards for the highest grades in Criminal Law and American Indian Law.

Sean already has a proven track record of success. He has a personable approach with clients and prides himself on hard work to obtain the best results for his clients.

Dr. Matthew Greife

Dr. Matthew Greife

Civil Rights Director

Dr. Greife passed the CA and CO bar exams in 2010 and since beginning the practice of law has earned two masters degrees and a PhD. Dr. Greife is primarily a criminal defense and civil rights attorney. Over his career Dr. Greife has secured numerous not guilty verdicts and sentences that are incredibly lenient for his clients. Additionally, he has convinced judges to give sentences that are below a mandatory minimum sentence – a feat very few criminal defense lawyers are able to accomplish. Dr. Greife is consistently retained as an expert witness for issues regarding sentencing, law enforcement culture and practices, the use of science in the law and the drafting of model legislation for environmental justice and social justice advocates.

On top of practicing law Dr. Greife has, or currently teaches, courses on criminology, law & society, corrections & punishment, environmental justice/crime, white collar and corporate crime and social control at Colorado State University. Furthermore, Dr. Greife is an active researcher that continues to publish articles in peer reviewed journals in order to promote the use of empirical data in legal decision making and the drafting of legislation. Below is a list of Dr. Greife’s publications.

Greife, Matthew J and Michael O. Maume (2019). “Do Companies Pay the Price for Environmental Crimes? Consequences of Criminal Penalties on Corporate Offend-ers.” https://link.springer.com.

Greife, Matthew J.; Paul B. Stretesky; Tara O’Conner-Shelly and Mark R. Pogrebin (2017). “Corporate Environmental Crime and Environmental Justice.” Criminal Justice Policy Review. 28(4): 327-346.

Goodrum, Sarah, Mark Pogrebin, Matthew Greife (2015). “Representing the Underdog: The Righteous Development of Death Penalty Defense Attorneys.” Criminal Law Bulletin. 51(2): 329-357. Reprinted in: Copes, Heath and Mark Pogrebin (2017). Voices from Criminal Justice: Insider Perspectives, Outsider Experiences. 2nd Ed.

Daniel C. Mossinghoff

Daniel C. Mossinghoff

Criminal Defense Director

I am Daniel Mossinghoff and I am proud to be the Criminal Defense Director for Baumgartner Law, LLC. I have been a criminal defense trial attorney for almost all of the 20 years I have been practicing. I am dedicated to protecting the rights of anyone accused of a crime and vindicating those wrongfully charged.

I graduated Magna Cum Laude from Regis University in 1996 and then graduated law school from the University of Colorado in 2000. As a fledging lawyer, I cut my teeth and learned trial work as a district attorney for four years. Fairly quickly, I realized I was not meant to work as a prosecutor and quit. I missed working with people and arguing to protect our Constitutional rights.

Since then, I have been a criminal defense attorney for the last 16 years. I have defended thousands of clients in the areas of DUI defense, juvenile law, domestic violence and major felony cases. I have tried over 150 jury trials and countless motions hearings. My former partner and I successfully defended a client charged with Murder in the 1st Degree. I have also presented or been published over a half dozen times in multiple areas of criminal defense. Finally, I have been recognized as a Rising Star by Superlawyers and received recognition by other ranking organizations. I am currently ranked 10/10 on AVVO.

I am invigorated to work with the legal team at Baumgartner Law, LLC. This firm intentionally created a team of lawyers who will work synergistically to give you the best defense available. I hope you will entrust your criminal matter with us.

Adam R. Yoast

Adam R. Yoast

Associate Attorney (Admission Pending)
Director of Media and Policy

Mr. Yoast has dedicated his life to advocating for those who are unable to advocate for themselves. Mr. Yoast prides himself on creating long-lasting, and meaningful relationship with those he represents within the law firm and in the community. As noted by his law school clinic professor, Mr. Yoast is beyond dedicated and “not only talks the talk, but also walks the walk.”

Mr. Yoast joined Baumgartner Law as a first year Associate Attorney who focuses on Constitutional Rights and Criminal Defense. He is also the firm’s Director of Media and Policy handling all aspects of public relations, coordinating with news outlets, managing the firm’s social media accounts, and organizing policy initiatives. Mr. Yoast is also currently a Legal Researcher for the Colorado Office of the Alternate Defense Counsel assisting attorneys on felony cases throughout Colorado.

Mr. Yoast is also a soon to be (February 2021) Board Member for Colorado Lawyers Helping Lawyers. He also currently acts a Development Consultant for Cut The Plastic EMS and End Game Association, Inc., which are establishing community programing here in Colorado and beyond.

Before joining the firm, Mr. Yoast started his career here in Colorado with the Colorado State Public Defender as a 2L Certified Intern in Arapahoe County and a Post-Graduate Deputy Public Defender in El Paso County. With the Public Defender, Mr. Yoast represented hundreds of clients on misdemeanor charges, completed several jury trials, and conducted dozens of motion hearings which focused on Constitutional issues.

Mr. Yoast is a graduate of CUNY School of Law he graduated with a 3.43GPA and completed four semesters in the number two ranked Criminal Defense Clinic in the country. While in clinic, Mr. Yoast represented individuals seeking clemency in New York; Mr. Yoast continues to help with his client’s case. Mr. Yoast also took courses on Race and the Law, Government Misconduct (Sec. 1983), First Amendment, Civil Disobedience, Bail Reform, and the Death Penalty. In addition to his Criminal Defense Clinic, Mr. Yoast also interned with Public Defender Service of the District of Columbia, Trial Division; American Civil Liberties Union, Campaign for Smart Justice; Brooklyn Defender Services, Mental Health Unit; and The Legal Aid Society of NYC, Juvenile Rights Practice, Special Litigation and Law Reform Unit.

Before attending law school, Mr. Yoast received a Master of Science in Ethics & Public Policy: Ethics & Policy of Race Relations where he graduated with a 3.97GPA and was the sole recipient of the department’s Academic Excellence Award. As part of the graduate program, Mr. Yoast also completed a Legal Internship with the Massachusetts Commission of Discrimination.

Mr. Yoast is originally from Northern California where he graduated from California State University, Sacramento, with a Bachelor of Arts degree in Philosophy: Applied Ethics & Law. While at Sac State, Mr. Yoast was a Justice Epstein Judicial Fellow, sat on several student government committees, was a Pre-Law Mentor for the Odyssey Mentor Program, and was a member of Phi Alpha Delta Law Fraternity. Mr. Yoast also completed a summer in residency with the King Hall Outreach Program/LSAC Pre-Law Scholarship Program at UC Davis School of Law. Mr. Yoast transferred to Sac State from America River College where he graduated with Associate of Arts degrees in Social Science and Liberal Arts.

Mr. Yoast believes in giving back to the community and has worked in a development capacity at several nonprofits while attending higher education. Most notably, Mr. Yoast worked at PowerMyLearning where he was responsible for volunteer and donor engagement while also implementing their program to distribute free computers to low-income students throughout NYC’s five boroughs. Mr. Yoast also worked on donor engagement with the Citizen Budget Commission, an organization which writes white-papers on NYC’s financials and advocates for responsible fiscal policy.

In his free time, Mr. Yoast enjoys hanging out with his Golden-doodle, playing disc-golf, rockhounding and fossil finding, creating art, and tending to his jungle of house plants.


  • J.D., CUNY School of Law
  • M.S., Ethics & Public Policy: Emphasis in Ethics & Policy of Race Relations, Suffolk University
  • B.A., Philosophy: Applied Ethics and Law, California State University, Sacramento
  • A.A. (2), Social Science and Liberal Arts, American River College


  • Bar Prep Scholarship, CUNY School of Law (2018-2019)
  • Michael Dickman Memorial Scholarship, Queens Country Bar Association (2018-2019)
  • Academic Excellence Award, Suffolk University (2012-2013)


  • Colorado Bar (Admission Pending)


  • Board Member, Colorado Lawyers Helping Lawyers (Expected February 2021)
  • Resident Guest & Development Consultant, End Game Association, Inc. Podcast & Organization
  • Development Consultant, Cut The Plastic Environmental Management Services

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