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. For six years, he investigated, tried, and handled appeals in a wide range of criminal cases. In the later part of his service, he worked on complex auto-theft and airport-theft matters involving organized criminal activity, racketeering issues, and electronic surveillance.

After leaving the District Attorney’s Office, Jonathan entered private practice in New York. Guardianship and protective proceedings have been a significant part of his work since then. He represented parties in proceedings involving the appointment of guardians for individuals alleged to be unable to manage their personal needs or financial affairs. He also served by court appointment as a Court Evaluator in New York City, a role similar to a Court Visitor in Colorado, investigating guardianship matters and reporting to the court.

Jonathan’s protective-proceedings experience includes work as counsel, fiduciary, and court appointee. He serves as a property guardian and as trustee of supplemental needs trusts. In Colorado, he has served as respondent’s counsel in protective proceedings and regularly represents professional and non-professional fiduciaries, including guardians, conservators, trustees, personal representatives, and agents acting under powers of attorney.

Jonathan represents clients in contested and uncontested guardianship and conservatorship matters, fiduciary litigation, probate disputes, trust disputes, estate administration disputes, and related elder law matters. These matters often involve capacity issues, family conflict, fiduciary authority, accountings, removal issues, care decisions, financial management, and court supervision. He brings to those matters courtroom experience and practical experience with the responsibilities fiduciaries face after appointment.

Jonathan believes many probate, trust, guardianship, conservatorship, and family disputes should be resolved through careful negotiation or mediation when a fair resolution is possible. These matters often involve family relationships, vulnerable persons, fiduciary duties, and assets that should not be depleted by unnecessary conflict. 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.

Jonathan moved to Colorado in 2003. Since then, he has continued to focus much of his practice on protective proceedings, probate and trust litigation, fiduciary matters, and related family and civil disputes.

Jonathan has written articles published in the Colorado Bar Association’s Colorado Lawyer and the Boulder County Bar Association newsletter. His Colorado Lawyer articles include “Estate of Everhart: Probate, Meet Civil” and “Omitted Spouse: Planning to Avoid Questions of Intent After Death,” both co-authored with Jessica H. Catlin. His Boulder County Bar Association newsletter articles include “Reformation to Correct Mistakes Under § 15-11-806, C.R.S.,” “Mental Capacity Standards,” and “Recovering Fees in Protective Proceedings,” co-authored with Brooke W. Brestel.

Jonathan also drafted two conservatorship chapters for A Probate Benchbook for Colorado Judges, a judicial resource made available to judges handling probate dockets. His chapters are titled “Authority and Responsibility of Conservator” and “Special Conservators.” The Benchbook addresses decedents’ estates, protective proceedings, powers of attorney, and fiduciary oversight.

Jonathan has presented to the Boulder County Bar Association on protective-proceedings topics, including capacity issues and the intersection of probate and domestic relations. He served as Chair of the Boulder County Bar Association’s Elder Law Section in 2017-2018. He volunteered at the Boulder County Court probate clinic, assisting unrepresented litigants with probate matters. He has also volunteered with the Boulder County Senior Law Clinic, which provides legal information and attorney advice to older adults and unrepresented community members on civil legal issues, including probate and related elder-law concerns.

Jonathan served as Chair of the Board of Directors of REACH Charter School in Denver, one of Colorado’s first fully inclusive schools, and served on the Board’s Governance Committee. He also serves as Secretary of a Denver-area nonprofit organization supporting children with Cluster B personality disorders and related needs.