9.1 Preliminary Investigations & Initial Response
Key Takeaways
- POST Unit VII.A, Preliminary Investigations, is a 6-hour required block and the foundation of the 46-hour Investigative Procedures unit.
- The preliminary investigation is everything the first officer does from dispatch to the point where the case is either closed or handed to a follow-up investigator.
- Priorities on arrival run life safety, threat, scene control, identification of witnesses and suspects, evidence preservation, and documentation — in that order.
- Separate witnesses before they speak to each other; contaminated accounts cannot be uncontaminated, and Colorado suppression practice will expose the contamination.
- The elements of the offense are the outline of the report: identify the statute at the scene and collect facts for each element while the scene is still available.
Preliminary Investigations & Initial Response
Unit VII.A — Preliminary Investigations (6 required hours) opens the 46-hour Investigative Procedures unit. POST treats the preliminary investigation as a patrol competency because in the overwhelming majority of Colorado agencies the patrol officer is the investigator: they take the report, work the scene, canvass, identify suspects, and either clear the case or hand it forward.
The operating premise is blunt. Cases are solved or lost in the first hour. Detectives inherit whatever the first officer preserved, and nothing more.
1. Response and Arrival Priorities
1. LIFE SAFETY - your own, then victims, bystanders, suspects
2. THREAT - is the suspect on scene, nearby, or gone?
3. SCENE CONTROL - boundaries, single entry point, log started
4. PEOPLE - identify and SEPARATE witnesses, victims, suspects
5. EVIDENCE - preserve first, collect second
6. DOCUMENTATION - notes, photographs, BWC, sketch
En route thinking. Use the drive to plan: what is the offense likely to be, what are the elements, what is the likely suspect direction of travel, what other units do you need, and what will you say in the first broadcast? Officers who arrive without a plan spend the first five minutes deciding what to do — the five minutes the suspect uses to leave.
2. Scene Control
Establish boundaries wider than you think you need; you can always shrink them. Designate one entry and exit path and start a crime scene log naming every person who enters, their agency, and their in and out times. Command staff, prosecutors and paramedics all belong on the log.
The log matters for two reasons: it identifies the source of any contamination later found, and it is the record that supports the officer's testimony about scene integrity. In Colorado suppression and trial practice, an unlogged scene is an invitation to argue that evidence was moved, added, or lost.
3. Witness Management
Separate first, interview second. Witnesses who talk to each other converge on a single account within minutes, and that convergence is irreversible. Physically separate them, place an officer or a barrier between them, and take independent accounts.
| Interview element | Practice |
|---|---|
| Sequence | Victim, then independent witnesses, then involved parties, then suspect |
| Open-ended first | "Tell me everything you remember from the beginning" — do not interrupt |
| Then clarify | Follow up on specifics only after the free narrative ends |
| Avoid contamination | Never feed a description or a name to a witness |
| Confidence statement | Record certainty in the witness's own words, at the time |
| Document identity | Full name, DOB, all phone numbers, employer, and a second contact |
Cognitive interview technique — asking the witness to mentally reinstate the context, report everything including apparently trivial detail, recall in a different order, and describe the event from another perspective — produces measurably more accurate detail than a question-and-answer format.
4. Identification Procedures
| Procedure | When | Requirements |
|---|---|---|
| Showup | Promptly after the offense, suspect detained nearby | Admonition that the person may or may not be the perpetrator; one witness at a time; no suggestive comments; document confidence verbatim |
| Photo array | Later, with a known suspect | Fillers matching the described characteristics; sequential or simultaneous per policy; ideally administered blind or blinded |
| Live lineup | Rare; usually post-filing | Right to counsel attaches after formal charges under United States v. Wade |
Suggestiveness is the failure mode. Bringing a witness to a suspect who is handcuffed beside a patrol car is inherently somewhat suggestive but is generally permitted when justified by promptness and necessity — provided the officer does not add commentary such as "we think this is the guy." One sentence like that can invalidate the identification.
5. The Neighborhood Canvass
A canvass is systematic, not casual:
- Define the canvass area by likely approach and escape routes, sightlines, and camera coverage — not by street address blocks.
- Knock every door in the area, and record no-answers for a return attempt.
- Ask about video first: doorbell cameras, business systems, dash cameras in parked vehicles, and building systems that overwrite in days.
- Ask what people heard as well as what they saw, and ask for times.
- Record everyone contacted with name and contact information, including those with nothing to report.
- Return at the same time of day as the offense to catch routine passers-by.
6. Solvability Factors
Most Colorado agencies screen cases for follow-up using solvability factors. Understanding them tells the patrol officer what to capture:
| Factor | Why it matters |
|---|---|
| Named or identifiable suspect | The single strongest factor |
| Suspect vehicle with a plate or partial | Immediately actionable |
| Usable physical evidence (latents, DNA, tool marks) | Database-searchable |
| Recoverable video | Increasingly the decisive factor |
| Traceable stolen property with serial numbers | Pawn and database hits |
| Distinctive MO | Links to series cases |
| Limited time window | Narrows suspects and video review |
A report that lacks all of these is usually inactivated. That is often not the offender's doing — it is the first officer's.
7. Report Structure Driven by Elements
Before leaving the scene, identify the Colorado statute and write the elements down. A second degree burglary report under C.R.S. 18-4-203, for example, must establish knowing entry, unlawfulness of the entry or the remaining, a building or occupied structure, and intent to commit a crime therein. If any element has no supporting fact, the officer is still at the scene and can still get it.
A complete Colorado patrol report answers: who reported it and when, what offense occurred with each element supported, when and where precisely, how the offender did it, what evidence exists and where it went, who the witnesses are and what each independently said, what the officer personally observed as distinct from what was reported, and what investigative steps remain. Attach the BWC file references. Under C.R.S. 24-31-902 the video exists whether the report mentions it or not, and any divergence between the two will be found.
An officer arrives at an armed robbery of a liquor store. Three customers witnessed the event and are standing together talking about what happened. What is the officer's most urgent investigative action regarding these witnesses?
A witness is brought to view a detained suspect at a showup approximately eight minutes after a street robbery. Which officer conduct would most likely render the identification inadmissible?