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Jonathan Leinheardt has practiced law since 1992. His practice focuses on probate litigation, trust and estate litigation, trust and estate administration, protective proceedings, fiduciary disputes, elder law, civil litigation, and domestic relations.
Jonathan began his legal career as an Assistant District Attorney in the Queens County District Attorney’s Office in New York City. After six years as a prosecutor, he entered private practice in New York, where guardianship and protective proceedings became a significant part of his work. He has continued that focus in Colorado since 2003.
Jonathan represents clients in contested and uncontested guardianship and conservatorship matters, probate disputes, trust disputes, fiduciary litigation, estate administration disputes, and related elder law matters. These cases often involve capacity issues, family conflict, fiduciary authority, accountings, removal issues, care decisions, financial management, and court supervision.
Jonathan regularly represents professional and non-professional fiduciaries, including guardians, conservators, trustees, personal representatives, and agents acting under powers of attorney. He has also served as respondent’s counsel in protective proceedings, as a Court Evaluator in New York City, as a property guardian, and as trustee of supplemental needs trusts. That experience gives him practical insight into the duties and challenges fiduciaries face.
Jonathan believes many probate, trust, guardianship, conservatorship, and family disputes should be resolved through careful negotiation or mediation when a fair resolution is possible. He works with clients to evaluate the costs, risks, benefits, and likely outcomes of litigation so they can make informed decisions. When a case cannot be settled because the other side is unreasonable, unfair, or unwilling to reach a workable resolution, Jonathan is prepared to advocate firmly for his client and ask the court to resolve the dispute.
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Practice Areas
30 years
30 years
22 years
30 years
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Chat withState: Colorado
Acquired: 2003
No misconduct found
State: New York
Acquired: 1992
No misconduct found
3825 Iris Ave, Suite 100, Boulder, CO, 80301
2 Client Reviews
Showing 1 - 1 of 1 review | Communication Style
Posted by Heather | January 17, 2026 | Hired Attorney
Jonathan is the lawyer you NEED!
If you want the absolute BEST attorneys your search ends here with Jessica Catlin and Jonathan Leinheardt at Strickler Catlin LLC. During what was undoubtedly one of the most difficult, devastating, challenging times of my life, this brilliant legal team proved to be invaluable. They are truly mast...
"I endorse this lawyer. He tenaciously represented a difficult client on a difficult case. While we were unable to reach a resolution, I respect his advocacy skills and legal acumen."
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2023 - Present
Attorney, Strickler Catlin LLC
2020 - 2023
Attorney, Hurth, Sisk & Blakemore
2019 - 2020
Partner, Stevens, Littman, Biddison, Tharp & Weinberg LLC
2007 - 2019
Associate, Stevens, Littman, Biddison, Tharp & Weinberg LLC
2004 - 2007
Associate, Stiner, Beck, Jonson & Nolan
1997 - 2003
Owner/Manager, Law Offices of Jonathan Leinheardt
1992 - 1997
Assistant District Attorney, Queens County District Attorney's Office
2006 - Present
Boulder County Bar AssociationFormer Co-Chair of Elder Law Committee
2004 - Present
U.S. District Court District of Colorado
2003 - Present
Colorado Bar Association
1993 - Present
U.S. District Court Eastern District of New York
1993 - Present
U.S. District Court Southern District of New York
1993 - Present
U.S. Court of Appeals 2nd Circuit
1991
JD
1988
BA - Bachelor of Arts
English