Colorado Adopts Four-Factor Test for Reasonableness of Delay Between Seizure and Search Warrant Application

Introduction

In People v. Mills, 2025 CO 47 (Colo. 2025), the Colorado Supreme Court resolved a recurring Fourth Amendment question: when police seize property based on probable cause with the intent to obtain a search warrant, how long may they lawfully hold the property before applying for the warrant? Rejecting a rigid “necessity” approach, the Court announced a new, statewide rule: a fact-intensive, four-factor balancing test to determine whether the delay in seeking a warrant was reasonable. Applying that test, the Court held that a three-day delay (spanning a weekend) between a vehicle’s seizure and the warrant application was reasonable on the facts presented.

The case arose from an undercover narcotics surveillance in Denver during which officers observed conduct they believed consistent with a drug transaction. After a traffic stop, officers seized the defendant’s Range Rover based on probable cause but deferred a full search until a warrant could be sought. An off-duty narcotics detective returned to work on Monday, arranged a K-9 sniff for Tuesday morning, and submitted a warrant application that afternoon. A judge issued the warrant shortly thereafter; the ensuing search revealed multiple controlled substances and scales. The district court suppressed the evidence, concluding the police unconstitutionally extended the seizure by waiting until Tuesday to apply for a warrant. The People sought interlocutory review under section 16-12-102(2), C.R.S., and C.A.R. 4.1.

The Colorado Supreme Court reversed, establishing a new doctrinal framework governing “seize-now, search-later” scenarios and clarifying that the touchstone remains reasonableness, not necessity.

Summary of the Opinion

The Court holds that when police seize property with probable cause intending to obtain a warrant, the constitutionality of any delay in seeking the warrant turns on reasonableness, assessed under a new four-factor balancing test:
1. Length of the delay;
2. Nature and strength of the individual’s possessory interest in the seized property;
3. Strength of the government’s justification for the delay; and
4. Government’s diligence in applying for the search warrant.
The Court rejects the trial court’s reliance on a “necessity” standard drawn from Chambers v. Maroney, clarifying that the Supreme Court’s Fourth Amendment analysis is grounded in reasonableness, not a least-possible-time or absolute-necessity rule.
Applying the new test, the Court finds the three-day delay reasonable in light of the weekend timing, the defendant’s comparatively weak possessory interest in the vehicle (no license or proof of insurance; other vehicles available), the government’s safety and investigative justifications (including arranging a K-9 sniff), and the detective’s overall diligence once back on duty.
Because the seizure was not rendered unconstitutional by the delay, suppression was improper. The Court reverses and remands. It does not reach the good-faith exception.

Analysis

Precedents Cited and Their Influence

The opinion carefully situates Colorado doctrine within U.S. Supreme Court and federal appellate precedent, emphasizing that the Fourth Amendment’s “ultimate touchstone” is reasonableness.

Chambers v. Maroney (U.S. 1970): The trial court read Chambers to impose a necessity limit—hold a car only as long as “necessary” to get a warrant. The Colorado Supreme Court corrects that reading. Chambers upheld a warrantless search at the station under the automobile exception and observed no constitutional difference between immediately searching a car with probable cause and seizing and holding it to present the matter to a magistrate. But Chambers did not analyze how long police may hold property before applying for a warrant. Thus, Chambers does not create a necessity standard for delay.
Illinois v. McArthur (U.S. 2001): McArthur upheld a temporary restraint on a suspect from re-entering his home while officers diligently sought a warrant, emphasizing reasonableness and diligence during a limited delay. The Court highlights McArthur’s language—“no longer than reasonably necessary” while acting diligently—as a reasonableness formulation, not a strict necessity rule.
United States v. Place (U.S. 1983): Place frames seizure reasonableness as a balance between the intrusion on possessory interests and governmental interests, a balance that informs this case’s framework.
Segura v. United States (U.S. 1984): A seizure reasonable at inception can become unreasonable due to its duration. This undergirds the need for a delay-focused analysis.
United States v. Burgard (7th Cir. 2012): Burgard is foundational. It distinguishes possessory interests (at issue during a seizure) from privacy interests (at issue during a search), instructing courts to weigh delay length, the owner’s possessory interests, and government diligence/justification. It warns against punishing deliberate, careful police work.
United States v. Smith (2d Cir. 2020): Smith emphasizes that once property is seized to obtain a warrant, officers have a time-sensitive duty to diligently apply for it; heavy caseloads alone do not justify extensive delays. Smith also details how to assess the owner’s possessory interest, especially with digital devices, and whether facts supporting probable cause were already known at the time of seizure.
United States v. Christie (10th Cir. 2013): Recognizes that competing investigative demands and case complexity can justify some delay; stresses the totality-of-circumstances approach.
United States v. Laist (11th Cir. 2012) and United States v. Mitchell (11th Cir. 2009): Illustrate that delays involving personal electronic devices implicate stronger possessory interests and require greater diligence.
United States v. Martin (2d Cir. 1998): An owner’s possessory interest may be diminished if property is voluntarily in the hands of a third party (e.g., parcel carriers), a nuance incorporated into Colorado’s new factor two.
United States v. Sullivan (9th Cir. 2015) and United States v. Hernandez (9th Cir. 2002): The Fourth Amendment does not require the least intrusive course or the earliest possible action; the measure remains reasonableness.
United States v. Sharpe (U.S. 1985): Courts should resist evaluating police conduct with “20/20” hindsight; the question is whether actions were reasonable, not whether one could imagine an even faster alternative.
Colorado cases: The Court cites People v. Thompson (reasonableness as touchstone), People v. McIntyre, People v. Davis, and People v. Deaner (standard of review). It also notes Colorado’s general coextensiveness with federal Fourth Amendment standards (Eddie’s Leaf Spring Shop & Towing v. PUC; People v. Rodriguez), with exceptions not implicated here (People v. McKnight). People v. Taylor and Delaware v. Prouse are cited to reaffirm reasonableness and protection against arbitrary invasions.

Together, these authorities paved the way for Colorado to adopt a structured, yet flexible, reasonableness test that mirrors the approach of several federal circuits while clarifying state law.

Legal Reasoning

The Court proceeds in three steps: reaffirm the reasonableness framework; select and synthesize the relevant factors; apply them to the facts.

Reasonableness, not necessity, governs. Because the Fourth Amendment prohibits unreasonable searches and seizures, the question is whether the time between seizure and warrant application was reasonable. The Court disapproves the trial court’s “only as long as necessary” formulation drawn from Chambers and harmonizes the analysis with McArthur’s emphasis on diligence and limited duration consistent with reasonableness.
The Four-Factor Balancing Test. Drawing heavily from Burgard and Smith, the Court adopts a totality-of-circumstances test that balances:
- Length of the delay: No bright-line rule. Longer delays increase intrusion on possessory interests; if officers had probable cause at seizure, they ordinarily should be able to articulate it promptly.
- Nature and strength of the individual’s possessory interest: Consider what the item is (e.g., vehicle vs. phone/laptop), how essential it is to daily life, and whether the person’s control was diminished (e.g., entrusted to a third party) or reasserted (e.g., requests for return). This factor focuses on possession, not privacy, because no search has occurred yet.
- Government’s justification for the delay: Assess objectively whether the delay was reasonable given the investigation’s complexity, safety considerations, resource realities, and competing demands. A bare claim of heavy workload is insufficient; articulable reasons matter.
- Government’s diligence: Officers have a time-sensitive duty to pursue the warrant without undue delay. At the same time, the law does not penalize careful, methodical police work that reasonably takes time.
The Court underscores that reasonableness does not compel the earliest conceivable filing or the least intrusive step; it rejects hindsight-driven perfection.
Application to Mills:
- Length: The delay was just under 72 hours and straddled a weekend. Courts have recognized weekends and holidays can explain some delay.
- Possessory interest: Although vehicles can be vital, Mills did not produce a valid driver’s license or proof of insurance for the Range Rover, and the record suggested access to other vehicles. The Court therefore viewed his possessory interest here as comparatively weaker. The Court also declined to reduce his interest based on possible civil forfeiture, noting forfeiture was not in play at the time of seizure.
- Justification: Officers faced safety and logistical considerations: the suspect refused to exit the car; no K-9 unit was immediately available; and the lead detective chose to bolster probable cause through a K-9 sniff before applying for a warrant. The Court endorses this “careful, attentive police work” and does not penalize the decision to corroborate probable cause before filing.
- Diligence: Although the detective mistakenly believed the vehicle could be held for up to seven days because warrants must be executed within seven days, his actions once back on duty were diligent: he requested a K-9 sniff Monday, conducted it Tuesday morning, and submitted the warrant that afternoon, incorporating all material facts (including the fresh K-9 alert). The Court emphasizes that the standard is not “earliest possible filing,” but reasonable diligence in context.
Weighing all four factors, the Court finds the delay reasonable and reverses suppression. Given that conclusion, the Court does not reach the good-faith exception.

Impact and Practical Implications

People v. Mills is a precedential recalibration for Colorado trial courts and law enforcement when property is seized on probable cause pending a warrant application. Key implications include:

Statewide rule: Colorado now has a clear, four-factor test governing delays between seizure and warrant application, aligning state practice with persuasive federal circuit authority (notably the Second and Seventh Circuits). Trial courts must conduct a structured, fact-specific reasonableness analysis rather than apply a necessity or per se timing rule.
No bright-line deadlines: There is no fixed outer limit (24, 48, 72 hours). Weekends and resource constraints can be relevant, but agencies should not treat this as a safe harbor. The inquiry remains case-specific.
Stronger scrutiny for personal electronics: Although this case involved a vehicle, the Court signaled that items like smartphones and laptops implicate stronger possessory interests. Future cases involving digital devices will likely demand heightened diligence and tighter timelines.
Documentation matters: Officers should contemporaneously document investigative steps (e.g., safety concerns, K-9 availability, drafting, coordination with prosecutors) to establish justification and diligence.
Defense strategy: Defendants should build a record of their possessory interest (e.g., essential use, lack of alternatives) and any reassertion of that interest (requests for return, checking status), and highlight when all probable-cause facts were known on day one. Unexplained periods of inactivity and “heavy caseload” claims without specifics will be vulnerable.
Avoiding misinterpretations: The seven-day period to execute a warrant does not grant a seven-day window to hold seized property before applying for a warrant. Agencies should update training to prevent similar misconceptions.
Automobile exception not penalized: Where officers could search immediately under the automobile exception but choose to seek a warrant, courts will not penalize cautious policing that reasonably extends time to seek judicial authorization—provided the delay is justified and diligent.

Complex Concepts Simplified

Seizure vs. search: A seizure interferes with possession of property (e.g., impounding a car). A search intrudes on privacy to find evidence (e.g., opening the car and backpack). The delay analysis here concerns the seizure phase, so courts focus on possessory interests, not privacy interests.
Probable cause: Facts and circumstances that would lead a reasonable person to believe evidence of a crime will be found in the place or item. Here, surveillance observations, the stop, and other behaviors supported probable cause to seize the vehicle pending a warrant.
Possessory interest: The owner’s right to control and use property. It is stronger when the item is essential to daily life (e.g., a sole means of transport) and weaker when legal or practical barriers prevent lawful use (e.g., lack of license/insurance), or when the item is already in the hands of a third party.
Interlocutory appeal under C.A.R. 4.1: Allows the prosecution to appeal certain suppression orders before trial, ensuring key evidentiary rulings are reviewed promptly.
Diligence: Reasonably prompt steps, consistent with investigative needs and available resources, to prepare and submit a warrant application. It does not require perfection or the fastest conceivable action, but it does require movement with purpose.
K-9 sniff: A trained dog’s alert can bolster probable cause for a search warrant. Waiting for a K-9 sniff can be a legitimate justification for brief delay if officers otherwise act diligently.
Good-faith exception: A doctrine that can save evidence from suppression if officers reasonably relied on a warrant later found invalid. The Court did not need to reach this issue because it found no Fourth Amendment violation.

Practice Pointers

For Law Enforcement

Document, at the time, why seizure without immediate search was necessary and what steps were taken toward a warrant.
Record practical constraints (weekends, unit availability, safety concerns) and what was done in the interim (drafting affidavits, contacting K-9 units, consulting prosecutors).
Do not assume warrant execution timelines equal permissible pre-application holding periods.
Prioritize digital devices for rapid warrant applications, given stronger possessory interests.

For Defense Counsel

Build the record on your client’s possessory interest: necessity of the item, lack of alternatives, and any requests for return.
Identify periods of unexplained inactivity and show that all facts material to probable cause were known immediately at seizure.
Differentiate cases involving vehicles from those involving personal electronics to leverage the second factor.

Conclusion

People v. Mills establishes a controlling framework for Colorado: when police seize property based on probable cause intending to obtain a warrant, courts will evaluate the reasonableness of any delay under a four-factor balancing test assessing delay length, the owner’s possessory interest, the government’s justification, and the government’s diligence. The decision rejects a rigid necessity or earliest-possible-action standard, endorsing a practical, totality-of-circumstances approach that discourages both foot-dragging and slapdash policing.

In applying its new test, the Court found the weekend-spanning, three-day delay reasonable where the defendant’s possessory interest in the vehicle was comparatively weak, safety and investigative considerations justified seeking a K-9 sniff, and officers acted diligently once back on duty. The ruling provides clear guidance to trial courts, law enforcement, and litigants, while leaving room for rigorous scrutiny in future cases—especially those involving personal electronic devices with heightened possessory interests.

Case Details

Citation: People v. Mills, 2025 CO 47, No. 24SA148 (Colo. June 30, 2025). Interlocutory appeal from the Denver District Court, Case Nos. 23CR4306 & 21CR6486. Opinion by Chief Justice Márquez, joined by all Justices.