5.1 Criminal Investigations

5.1 Criminal Investigations

The uniformed officer who arrives first often determines whether a case can be prosecuted months later. North Carolina's BLET Criminal Investigations block (40 hours — typically 24 lecture and 16 practical) trains entry-level officers to run a competent preliminary investigation, protect scenes, preserve evidence, and hand a clean case file to detectives or the North Carolina State Bureau of Investigation (SBI) when needed. This section mirrors that Module II priority: investigations come first, then victim response.

Preliminary Investigation: What the First Officer Owns

A preliminary investigation is the initial fact-finding and scene work performed by the responding officer before specialized investigators take over. It is not a finished homicide package — it is the foundation every later investigator will depend on.

Core first-officer steps, in order of priority:

1. Make the scene safe — address active threats, render aid, and request EMS, fire, or additional units.
2. Secure and protect the crime scene — establish a perimeter large enough to protect fragile evidence; expand it if needed.
3. Identify and separate witnesses — keep witnesses from comparing stories; obtain identifying information immediately.
4. Identify and protect physical evidence — note locations before anything is moved; photograph or document in place when possible.
5. Conduct a brief initial canvass — locate additional witnesses and surveillance cameras while memories are fresh.
6. Document everything — times, weather, lighting, who entered the scene, and what changed before you arrived.
7. Notify supervision / detectives — especially for death investigations, serious assaults, sexual assaults, robberies, and major property crimes per agency policy.

BLET trap: The exam often frames "investigation" as something only detectives do. Entry-level patrol officers are investigators during the preliminary phase. Skipping documentation because "detectives will handle it" is a classic failure point.

Crime Scene Protection

Scene integrity is the difference between usable evidence and courtroom disaster. Protect the scene by:

• Establishing an inner perimeter around the core evidence area and an outer perimeter for staging, command, and media control.
• Creating a single entry/exit path when possible and logging everyone who enters.
• Keeping unauthorized persons — including curious officers — out.
• Preserving transient evidence (shoe prints in soft dirt, blood patterns that rain will destroy, spent casings that can be kicked).
• Treating the victim's body and the area around it as evidence until the medical examiner / death investigator releases the scene.

Do not clean, rearrange furniture "to help," or allow family members to "just grab a few things" from inside a secured scene. Compassion belongs outside the tape; contamination happens inside it.

Chain of Custody and Evidence Types

Chain of custody is the continuous, documented record of every person who collected, handled, transferred, stored, or analyzed an item of evidence from seizure to courtroom. Breaks in the chain give the defense a powerful attack even when the science is sound.

Practical rules officers must internalize:

• Mark, package, and seal evidence properly; wet biological evidence generally goes in breathable paper, not sealed plastic.
• Label every package with case number, item number, date/time, collector identity, and a seal that shows any reopening.
• Minimize handlers — every extra hand is another witness the state may need.
• Never leave evidence unsecured in a patrol car trunk "just for a minute" without logging and agency-compliant storage.

Evidence categories you will see on BLET-style questions:

Canvassing and Case File Building

A canvass is a systematic door-to-door or area search for witnesses, video, and leads. Do it early: people leave, cameras overwrite, and memories fade. Ask open questions ("What did you see or hear?") before narrowing. Note negative results ("Apartment 4B home, saw nothing") — negatives help detectives understand coverage.

Your case file should let a detective who was never on scene reconstruct the night. Include:

• Initial call information and times (dispatch, arrival, scene secured)
• Victim/witness statements and contact data
• Crime-scene sketch, photos, body-worn camera references
• Evidence inventory and custody forms
• Suspect description, vehicle info, and any BOLO issued
• Notifications made (supervisor, detective, SBI, medical examiner)

Coordinating with Detectives and the SBI

Patrol does the preliminary work; detectives deepen it. Know when to call for help: complex death scenes, officer-involved shootings, child sexual abuse in daycare settings, major drug trafficking, election-law or environmental crimes, and other matters where the North Carolina SBI has specialized capacity or original jurisdiction. Local agencies routinely request SBI assistance for crime-scene processing and laboratory analysis. The NC State Crime Laboratory examines evidence free of charge for public NC law-enforcement agencies — but only if packaging, seals, and submission paperwork meet lab standards.

Coordination principles: preserve first, consult early, do not freelance specialty processing you are not trained to do, and never discard potential evidence because it "doesn't look important."

Common BLET Exam Traps

• Confusing preliminary investigation duties with "waiting for CID."
• Treating chain of custody as optional paperwork rather than courtroom survival.
• Packaging biological evidence incorrectly.
• Focusing only on the suspect and ignoring witness separation and canvass.
• Moving evidence before documentation "to keep it safe."
• Assuming SBI automatically takes every serious case — local officers remain responsible until properly relieved.

Master the preliminary investigation and you protect victims, support prosecutors, and avoid the most predictable exam and field failures.