4.3 Investigatory Stops (Stone/Terry), Reasonable Suspicion & Probable Cause

Investigatory Stops (Stone/Terry), Reasonable Suspicion & Probable Cause

In daily law enforcement operations, peace officers interact with citizens across a spectrum of encounters. The United States Supreme Court and the Colorado Supreme Court have established a strict tripartite hierarchy of police-citizen contacts. Accurately identifying which tier an encounter occupies is critical: an officer who treats a consensual encounter as a detention, or who escalates an investigatory stop into a de facto arrest without probable cause, commits an unconstitutional seizure that invalidates all resulting evidence.

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1. The Three Tiers of Police-Citizen Encounters in Colorado

+-------------------------------------------------------------------------+
|                 THE THREE TIERS OF POLICE-CITIZEN CONTACTS              |
|                                                                         |
|   TIER 1: CONSENSUAL CONTACT                                            |
|   * Legal Standard: ZERO SUSPICION REQUIRED                             |
|   * Test: Reasonable person feels free to leave or decline to answer    |
|   * Scope: Casual questioning, asking for ID without retention          |
|                                   │                                     |
|                                   ▼ (Officer Commands / Restraint)      |
|   TIER 2: INVESTIGATORY STOP (Stone / Terry Stop)                       |
|   * Legal Standard: REASONABLE ARTICULABLE SUSPICION (RAS)              |
|   * Test: Stone v. People 3-Prong Test; temporary detention             |
|   * Scope: Brief, diligent inquiry; Frisk ONLY if armed & dangerous     |
|                                   │                                     |
|                                   ▼ (Full Physical Restraint / Custody) |
|   TIER 3: FULL CUSTODIAL ARREST                                         |
|   * Legal Standard: PROBABLE CAUSE (PC)                                 |
|   * Test: Prudent person belief crime committed by arrestee             |
|   * Scope: Full booking, jail confinement, search incident to arrest    |
+-------------------------------------------------------------------------+

Comprehensive Three-Tier Comparison Grid

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2. Tier 1: Consensual Contacts

A consensual contact occurs when an officer approaches a citizen in a public space, engages in conversation, asks questions, or asks for identification, provided the officer does not convey a message that compliance with the request is required.

The Free-to-Leave Objective Test

Under United States v. Mendenhall, 446 U.S. 540 (1980), Florida v. Bostick, 501 U.S. 429 (1991), and People v. Cascio, 711 P.2d 1240 (Colo. 1985), an encounter remains consensual as long as a reasonable person in the citizen's position would feel free to disregard the police, terminate the encounter, or leave at will.

Factors That Convert a Consensual Contact into an Unconstitutional Seizure

• Threatening presence of multiple officers surrounding the individual;
• Display of a firearm or weapon by an officer;
• Physical touching, grabbing, or holding of the person;
• Authoritative tone of voice or language indicating that compliance is mandatory ("Stop right there, don't move");
• Positioning patrol cruisers to block the citizen's vehicle path or pedestrian exit route;
• Activating emergency overhead red/blue lights (spotlights or takedown lights may be permissible depending on context);
• Retaining citizen documents: Taking a person's driver's license or passport and walking back to the patrol vehicle converts a consensual contact into an investigatory detention because a reasonable person cannot leave without their legal identification.

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3. Tier 2: Investigatory Stops (Colorado "Stone Stops")

In federal jurisprudence, an investigatory detention is governed by Terry v. Ohio, 392 U.S. 1 (1968). In Colorado, state law is anchored by the landmark Colorado Supreme Court decision in Stone v. People, 485 P.2d 495 (Colo. 1971) and codified in C.R.S. § 16-3-103.

                    THE COLORADO STONE STOP THREE-PRONG TEST
                            (Stone v. People, 1971)

   ┌─────────────────────────────────────────────────────────────────────────┐
   │ PRONG 1: ARTICULABLE BASIS IN FACT                                      │
   │ The officer must possess an articulable and specific basis in fact for  │
   │ suspecting that criminal activity has occurred, is occurring, or is     │
   │ about to occur. (Reasonable Articulable Suspicion - RAS).               │
   └────────────────────────────────────┬────────────────────────────────────┘
                                        │
                                        ▼
   ┌─────────────────────────────────────────────────────────────────────────┐
   │ PRONG 2: REASONABLE PURPOSE OF INTRUSION                                │
   │ The purpose of the stop must be reasonable (e.g., determining identity, │
   │ verifying explanation of suspicious behavior, checking warrants).       │
   └────────────────────────────────────┬────────────────────────────────────┘
                                        │
                                        ▼
   ┌─────────────────────────────────────────────────────────────────────────┐
   │ PRONG 3: REASONABLE SCOPE AND CHARACTER                                 │
   │ The scope and character of the intrusion must be reasonable when        │
   │ considered in light of the purpose (duration, movement, force).         │
   └─────────────────────────────────────────────────────────────────────────┘

Reasonable Articulable Suspicion (RAS) Defined

Reasonable suspicion is a standard less demanding than probable cause, but substantially higher than an unparticularized hunch or generalized suspicion. It requires specific, articulable facts that, taken together with rational inferences from those facts, give rise to a reasonable suspicion that the person stopped has committed, is committing, or is about to commit a crime.

Factors Establishing RAS (Totality of Circumstances)

• High-Crime Area + Unprovoked Flight: Illinois v. Wardlow, 528 U.S. 119 (2000): Presence in a high-crime area alone is insufficient, but unprovoked, headlong flight upon seeing uniformed police in a high-crime area justifies an investigatory stop.
• Informant Tips: Alabama v. White, 496 U.S. 325 (1990) (anonymous tip predicting future behavior, corroborated by police observation, establishes RAS) vs. Florida v. J.L., 529 U.S. 266 (2000) (bare anonymous tip stating a young man in a plaid shirt at a bus stop has a gun, lacking predictive corroboration, is insufficient for an investigatory stop or frisk).
• Furtive Movements & Temporal Proximity: Matching suspect description near a recently reported robbery scene at 3:00 AM.

Scope and Duration Limits: Rodriguez v. United States

Under United States v. Sharpe, 470 U.S. 675 (1985) and Rodriguez v. United States, 575 U.S. 348 (2015), an investigatory stop must last no longer than is necessary to effectuate the mission of the stop. In a routine traffic stop, once the mission of checking license, registration, insurance, and issuing the ticket or warning is complete, officers cannot prolong the detention for dog sniffs or unrelated criminal questioning without independent reasonable suspicion.

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4. Protective Weapons Frisks & The Plain Feel Doctrine

A critical rule of constitutional law is that the authority to stop does NOT automatically confer the authority to frisk.

                  STOP vs. FRISK: THE CRITICAL DIVIDE

   INVESTIGATORY STOP (Stone/Terry)     PROTECTIVE WEAPONS FRISK
   * Standard: RAS of ANY crime         * Standard: Independent RAS that the
     (theft, trespass, vandalism).        suspected person is ARMED & DANGEROUS.
   * Purpose: Investigate crime.        * Purpose: Officer safety ONLY.
   * Scope: Temporary detention.        * Scope: Pat-down of OUTER clothing for
                                          hard objects (weapons).

Requirements for a Lawful Protective Frisk

1. Lawful Stop: The initial stop must be constitutional under Stone/Terry.
2. Reasonable Belief of Armed and Dangerous: The officer must have specific, articulable facts that lead to a reasonable belief that the suspect is armed and presently dangerous (Terry v. Ohio).
   • Factors: Nature of suspected crime (e.g., armed robbery, violent assault inherently suggest weapons; shoplifting does not), visible weapon bulges, suspect reaching into waistband, aggressive threats.
3. Scope of the Frisk: Strictly confined to a careful pat-down of the suspect's outer clothing to detect concealed weapons (guns, knives, clubs). An officer cannot reach into pockets or manipulate soft objects unless a hard, weapon-like object is felt.

The Plain Feel Doctrine: Minnesota v. Dickerson

Under Minnesota v. Dickerson, 508 U.S. 366 (1993), if a peace officer conducting a lawful, non-coercive pat-down for weapons feels an object whose contour or mass makes its illicit character immediately apparent as contraband without any squeezing, sliding, rolling, or further manipulation, the officer may reach into the clothing and seize it.

[!CAUTION] If an officer pats an outer jacket, feels a small, soft lump, and squeezes, rubs, and manipulates it between their fingers for several seconds before deciding it feels like crack cocaine in a plastic baggie, the officer has exceeded the permissible scope of a Terry frisk under Dickerson, and the evidence will be suppressed.

5. Tier 3: Full Custodial Arrest & Probable Cause

A full custodial arrest is a permanent or significant deprivation of liberty where a person is taken into custody and processed through the criminal justice system.

Probable Cause Defined

Probable cause exists when the facts and circumstances within the officer's knowledge, and of which they have reasonably trustworthy information, are sufficient in themselves to warrant a person of reasonable caution in the belief that an offense has been or is being committed by the person to be arrested (Beck v. Ohio, 379 U.S. 89 (1964); People v. Tottenhoff, 691 P.2d 340 (Colo. 1984)).

                      PROBABLE CAUSE vs. REASONABLE SUSPICION

   0% Suspicion              25%-35% Suspicion             >50% Probability
   ┌───────────────────────────────┬───────────────────────────────┐
   ▼                               ▼                               ▼
CONSENSUAL CONTACT          REASONABLE SUSPICION            PROBABLE CAUSE
(No Seizure)                (Stone / Terry Stop)           (Custodial Arrest / Search Warrant)
* Zero suspicion needed     * Specific, articulable facts   * Fair probability of guilt / evidence
* Free to walk away         * Crime afoot + armed/dangerous * Substantial objective basis

Warrantless Arrest Authority under Colorado Statute: C.R.S. § 16-3-102

Under C.R.S. § 16-3-102, a Colorado peace officer may arrest a person without a warrant under the following specific statutory circumstances:

1. Warrant Outstanding: When a valid warrant for the person's arrest has been issued and is outstanding;
2. Crime in Presence (C.R.S. § 16-3-102(1)(b)): When any criminal offense (felony, misdemeanor, or petty offense) has been or is being committed by such person in the officer's actual presence;
3. Probable Cause for Felony (C.R.S. § 16-3-102(1)(c)): When the officer has probable cause to believe that a felony was committed and that the person to be arrested committed it, regardless of whether it occurred in the officer's presence;
4. Probable Cause for Misdemeanor (C.R.S. § 16-3-102(1)(d)): When the officer has probable cause to believe that a misdemeanor was committed, and:
   • The officer has reason to believe that the suspect will not be apprehended unless immediately arrested;
   • The officer has reason to believe the suspect may cause injury to self or others or damage to property;
   • The suspect refuses to identify themselves or sign a summons; OR
   • A specific statutory mandatory arrest provision applies (e.g., Domestic Violence mandatory arrest under C.R.S. § 18-6-803.6).

Petty Offense Mandatory Summons Rule (C.R.S. § 16-3-105)

Under Colorado statutory law, peace officers are generally required to issue a penalty assessment or Summons and Complaint in lieu of custodial arrest for petty offenses, unless the suspect refuses to sign the promise to appear, fails to provide satisfactory identification, or presents an immediate physical danger.

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6. Constitutional Use of Force During Stops & Arrests

Every use of force by a peace officer to effect an investigatory stop or custodial arrest constitutes a seizure subject to the Fourth Amendment's reasonableness standard.

The Graham v. Connor Objective Reasonableness Standard

In Graham v. Connor, 490 U.S. 386 (1989), the U.S. Supreme Court established that the reasonableness of a peace officer's use of force must be judged from the perspective of a reasonable officer on the scene, rather than with the 20/20 vision of hindsight. The court evaluates the "Graham Factors":

1. The severity of the crime at issue;
2. Whether the suspect poses an immediate threat to the safety of officers or others; and
3. Whether the suspect is actively resisting arrest or attempting to evade arrest by flight.

[!IMPORTANT] Under Colorado statutory reforms (C.R.S. § 18-1-707 and SB 20-217), Colorado peace officers may apply physical force only when non-violent means have been exhausted or are clearly futile, and must use only that degree of force that is proportional and objectively reasonable to effect the arrest or detention, with a strict statutory prohibition against chokeholds and neck restraints.