CGIA Notice Period Runs from Injury Discovery—Not Identification of the Liable Public Entity; Strict Compliance Required Absent Misleading by the Noticed Entity

Case: Mostellar v. City of Colorado Springs, 587 P.3d 168, 2026 CO 22 (Colo. 2026) (Gabriel, J.)
Court: Colorado Supreme Court (en banc)
Date: April 13, 2026

1. Introduction

Mostellar v. City of Colorado Springs addresses a recurring and consequential Colorado Governmental Immunity Act (“CGIA”) problem: what happens when an injured claimant timely notifies one public entity, but later learns (after the 182-day window) that a different public entity may actually be responsible—here, due to an undisclosed intergovernmental agreement?

Parties and setting. Petitioner Jaimi J. Mostellar alleged she tripped and fell on a public sidewalk in Manitou Springs on August 26, 2021, over the base of a removed bus stop sign. She timely served CGIA notice on the City of Manitou Springs. Roughly a year and a half later, Manitou Springs first informed her that an intergovernmental agreement made the City of Colorado Springs responsible for the sign/sidewalk condition. Mostellar then served notice on Colorado Springs—602 days after the injury.

Key issues. The Colorado Supreme Court granted certiorari to decide:

• Whether the CGIA’s notice period in section 24-10-109(1) began when Mostellar learned of the intergovernmental agreement (and thus Colorado Springs’ potential liability), rather than when she was injured; and
• Whether strict compliance should be excused when strict compliance is “impossible” because one public entity fails to inform the claimant that another public entity may be liable.

2. Summary of the Opinion

The Court affirmed the court of appeals’ judgment requiring dismissal for lack of subject matter jurisdiction.

• Strict compliance required. Section 24-10-109(1) is unambiguous: notice must be filed within 182 days after discovery of the injury, and compliance is a jurisdictional prerequisite. Because it is a non-claim statute, it is not subject to equitable defenses such as waiver, tolling, or estoppel.
• No “impossibility” or “misleading defendant” exception on these facts. Colorado Springs did nothing to prevent timely notice. Any alleged nondisclosure by Manitou Springs was “irrelevant” to Mostellar’s statutory duties to Colorado Springs. The Court also found Mostellar did not substantiate “impossibility” because she did not show why she could not have pursued other avenues (e.g., open records) to identify Colorado Springs’ role.
• Notice clock began on August 26, 2021. Mostellar knew of her injury that day; therefore, the notice window ran from that date, not from later discovery of Colorado Springs’ potential involvement.

3. Analysis

3.1 Precedents Cited

Trinity Broad. of Denver, Inc. v. City of Westminster, 848 P.2d 916 (Colo. 1993)

Role in the Opinion. Trinity Broad. of Denver, Inc. v. City of Westminster supplies the modern articulation of the CGIA notice trigger after the legislature’s 1986 amendment: the notice period begins when the claimant has discovered they were “wrongfully injured,” and the claimant “need not yet know the cause of the injury or the extent of the damage.”

How it influenced the decision. The Court relied on Trinity to reject Mostellar’s attempt to tie the notice clock to later discovery of Colorado Springs’ potential liability. Trinity anchors the Court’s statutory reading that injury discovery—rather than the full legal picture—starts the 182-day period.

State v. Young, 665 P.2d 108 (Colo. 1983)

Role in the Opinion. The district court relied on State v. Young for the idea that a claimant must have a “reasonable opportunity to discover the basic and material facts” underlying a claim before CGIA notice obligations attach.

How it influenced (and was limited in) the decision. The Supreme Court treated Young as superseded for purposes of section 24-10-109(1) by the legislature’s 1986 amendment. The Court reinforced that the amendment “override[d]” Young by making clear that notice runs from discovery of injury “regardless of whether the person then knew all of the elements of a claim.”

Reg'l Transp. Dist. v. Lopez, 916 P.2d 1187 (Colo. 1996)

Role in the Opinion. Reg'l Transp. Dist. v. Lopez is cited for the proposition that the 1986 amendment was designed to override the pre-amendment approach associated with Young.

How it influenced the decision. The Court used Lopez to situate its holding within the legislature’s corrective choice: to foreclose arguments that the notice period waits for discovery of “legal theory” or other claim elements.

Mesa Cnty. Valley Sch. Dist. No. 51 v. Kelsey, 8 P.3d 1200 (Colo. 2000)

Role in the Opinion. This is the Court’s primary authority for two propositions: (1) a claimant’s failure to comply with section 24-10-109(1) requires dismissal for lack of subject matter jurisdiction; and (2) section 24-10-109(1) is a non-claim statute not subject to equitable defenses like waiver, tolling, or estoppel.

How it influenced the decision. Mesa Cnty. supplies the jurisdictional consequence that makes the timing question dispositive. Once the Court determined the clock started at injury discovery, Mesa Cnty. compelled dismissal.

City & Cnty. of Denver v. Crandall, 161 P.3d 627 (Colo. 2007)

Role in the Opinion. The Court cited City & Cnty. of Denver v. Crandall to confirm and reinforce that section 24-10-109(1), as a non-claim provision, is not subject to equitable defenses.

How it influenced the decision. This citation strengthens the Court’s refusal to import equitable tolling/estoppel to address the claimed unfairness created by intergovernmental arrangements and late disclosure.

Finnie v. Jefferson County School District R-1, 79 P.3d 1253 (Colo. 2003)

Role in the Opinion. Mostellar’s central fairness argument leaned on Finnie v. Jefferson County School District R-1, where the Court applied a “substantial compliance” approach in the context of section 24-10-109(3) (the “where to file” requirement) after a public entity misdirected counsel about proper filing.

How it influenced the decision (by contrast). The Court used Finnie to draw a bright doctrinal line:

• Section 24-10-109(1) (timing) is a “jurisdictional prerequisite” requiring strict compliance.
• Section 24-10-109(3) (place/manner of filing) is treated as a “statutory defense,” permitting case-by-case evaluation and “substantial compliance,” including equitable/agency considerations and protection against governmental misrepresentation.

On the facts, the Court further distinguished Finnie because the entity entitled to notice there (the school district) affirmatively misled counsel; here, Colorado Springs did not mislead or impede Mostellar at all.

Jefferson Cnty. Health Servs. Ass'n v. Feeney, 974 P.2d 1001 (Colo. 1998)

Role in the Opinion. Jefferson Cnty. Health Servs. Ass'n v. Feeney is cited for the policy purposes behind CGIA notice: prompt investigation and remediation, encouraging settlement, fiscal planning, and preparation of defenses.

How it influenced the decision. The Court invoked these purposes to rebut Mostellar’s “absurd results” argument, emphasizing that the legislature chose administrable strict deadlines to serve governmental planning and response functions.

City of Boulder v. Pub. Serv. Co. of Colo., 2018 CO 59, 420 P.3d 289

Role in the Opinion. This case is cited for the standard of review: de novo review of a C.R.C.P. 12(b)(1) ruling when the dispute concerns characterization of the complaint rather than contested jurisdictional facts.

Pub. Serv. Co. of Colo. v. Outdoor Design Landscaping LLC, 2026 CO 6, 583 P.3d 778

Role in the Opinion. It is used for general statutory construction methodology (plain meaning; ambiguity analysis; when to consult extrinsic aids).

Mostellar v. City of Colo. Springs, No. 23CA1908 (Oct. 24, 2024)

Role in the Opinion. The Supreme Court affirmed the division’s result and much of its reasoning, including the emphasis that the CGIA deadline is jurisdictional and not subject to tolling or estoppel, and the division’s point that Young predates and was displaced by the 1986 statutory amendment.

Notable feature. The Supreme Court acknowledged the special concurrence’s policy concern (Judge Freyre) but treated remedy as a matter for the legislature, not judicial modification of section 24-10-109(1)’s text.

3.2 Legal Reasoning

(a) The Court’s interpretive anchor: the text of section 24-10-109(1)

The Court treated section 24-10-109(1) as unambiguous. Two textual choices control the outcome:

• The notice must be filed “within one hundred eighty-two days after the date of the discovery of the injury”; and
• this is required “regardless of whether the person then knew all of the elements of a claim or of a cause of action for such injury.”

That second clause does the key work in this dispute: it forecloses attempts to postpone the notice trigger until the claimant learns additional “elements” (e.g., which entity is legally responsible under an intergovernmental agreement).

(b) Jurisdictional and non-claim consequences

Relying on Mesa Cnty. Valley Sch. Dist. No. 51 v. Kelsey and City & Cnty. of Denver v. Crandall, the Court reiterated that section 24-10-109(1):

• is jurisdictional (noncompliance deprives courts of subject matter jurisdiction); and
• is a non-claim statute (equitable doctrines like tolling/estoppel do not apply).

This doctrinal framing compresses the analysis. Once untimeliness is found, dismissal is mandatory rather than discretionary.

(c) Rejecting a “responsible-entity discovery” trigger

The Court explicitly rejected the district court’s approach (derived from State v. Young) that the notice clock starts when the claimant learns “who caused” the injury. The Court reasoned that:

• Young was overridden by the 1986 amendment (as described in Reg'l Transp. Dist. v. Lopez);
• modern cases like Trinity Broad. of Denver, Inc. v. City of Westminster hold the period begins upon discovery of wrongful injury, not upon complete knowledge of claim elements.

(d) Limiting “substantial compliance” to section 24-10-109(3) and to misleading by the noticed entity

The Court gave Finnie v. Jefferson County School District R-1 a confined role: it authorizes substantial compliance for section 24-10-109(3) (where to file notice), particularly to prevent a public entity from benefitting from its own misrepresentation about compliance.

But the Court refused to use Finnie to soften section 24-10-109(1)’s timing rule—especially where:

• Colorado Springs did not mislead Mostellar; and
• the complained-of nondisclosure was by Manitou Springs, a different public entity.

The opinion thereby crystallizes an entity-specific fairness principle: even if misrepresentation might matter in some contexts, it must be attributable to the entity entitled to notice, not a third party.

(e) Disposing of “impossibility” and “absurd results”

The Court treated “impossibility” as both factually unsupported and legally insufficient on this record. It noted Mostellar did not explain why she could not have used investigative tools (e.g., an open records request or researching how local transit/stop infrastructure is organized) that might have uncovered Colorado Springs’ involvement.

On “absurd results,” the Court held there is no absurdity in enforcing the legislature’s clear rule, and it tied strict enforcement to the CGIA’s policy goals as stated in Jefferson Cnty. Health Servs. Ass'n v. Feeney.

3.3 Impact

(a) Practical impact on claimants and counsel

• Identify and notice multiple entities early. The opinion incentivizes “belt-and-suspenders” noticing: when injuries occur on or near public infrastructure, claimants may need to provide CGIA notice to every plausibly responsible public entity within 182 days, even if ultimate responsibility is uncertain.
• Intergovernmental agreements do not extend the clock. A claimant cannot rely on the later disclosure of an intergovernmental agreement to restart or toll the 182-day period under section 24-10-109(1).
• Investigation must occur within the CGIA window. The Court’s discussion of open records requests and research signals that diligence expectations may be argued in future cases to defeat “impossibility” narratives.

(b) Doctrinal impact on CGIA litigation

• Reinforces the post-1986 regime. The opinion tightens the connection between the statutory text (“discovery of the injury”) and the trigger date, further distancing modern CGIA notice law from pre-amendment concepts associated with State v. Young.
• Clarifies the boundary of Finnie. It emphasizes that “substantial compliance” and misrepresentation-protection reasoning are tethered to section 24-10-109(3), not the timing requirement in section 24-10-109(1), and in any event require conduct by the entity entitled to notice.
• Limits cross-entity equity arguments. The Court’s statement that misconduct by Manitou Springs was “irrelevant” to duties owed to Colorado Springs signals resistance to “agency-by-governmental-network” theories absent statutory authorization.

(c) Institutional/policy impact

Echoing the court of appeals’ concurrence, the Court acknowledged the outcome may seem harsh where the claimant acted in good faith and one public entity delayed disclosure. But it treated any corrective mechanism as legislative. This invites (and may accelerate) legislative consideration of whether section 24-10-109(1) should be amended to address intergovernmental opacity or strategic nondisclosure.

4. Complex Concepts Simplified

• CGIA “notice of claim” (section 24-10-109(1)). A written notice that must be sent to the public entity within 182 days after the claimant discovers the injury. It is a prerequisite to suing under the CGIA.
• Non-claim statute. A deadline that extinguishes the claim itself if missed (not merely a defense that can be waived). Here, missing the deadline “forever bar[s]” the action.
• Jurisdictional prerequisite / subject matter jurisdiction. If the prerequisite is not met, the court lacks power to hear the case against that entity; the case must be dismissed regardless of merits.
• Strict compliance vs. substantial compliance. “Strict” means meeting the statute exactly (timely notice within 182 days). “Substantial” means close-enough compliance may suffice in limited contexts. The Court explained substantial compliance applies (if at all) to section 24-10-109(3) (where to file), not section 24-10-109(1) (when to file).
• Equitable tolling / estoppel. Judge-made doctrines that can pause or prevent assertion of a deadline when fairness requires. The Court reaffirmed these doctrines do not apply to section 24-10-109(1).
• Discovery rule (as used here). Not the common “discover the cause/defendant” rule. Under section 24-10-109(1), the relevant “discovery” is discovery of the injury—“regardless” of whether the claimant knows all claim elements (including which entity is responsible).
• Intergovernmental agreement. A contract between public entities allocating responsibility. This case holds that such an agreement (and late disclosure of it) does not postpone the CGIA’s notice clock.

5. Conclusion

Mostellar v. City of Colorado Springs reaffirms—and sharpens—the CGIA’s timing rule: the 182-day notice period in section 24-10-109(1) begins when the claimant discovers the injury, not when the claimant later discovers which public entity may be legally responsible. The Court also narrows the practical reach of equitable and misrepresentation-based arguments by emphasizing that (1) section 24-10-109(1) demands strict compliance as a jurisdictional prerequisite, and (2) any alleged nondisclosure by a different public entity does not excuse late notice to the entity entitled to notice.

The decision’s significance lies less in doctrinal novelty than in its clear guidance for future CGIA practice: when governmental responsibility is uncertain, claimants must investigate quickly and provide timely notice broadly, because courts will not extend section 24-10-109(1)’s deadline to account for later-discovered intergovernmental allocations of responsibility.