Securing the scene is the responsibility of the first-responding law-enforcement officer (first responder). The safety of all individuals in the area is the first priority. Preservation of evidence is the second priority. This means the officer protects the area within which the crime has occurred, restricting all unauthorized persons from entering. Transfer, loss, or contamination of evidence can occur if the area is left unsecured (Locard’s Principle of Exchange). The first officer on the scene keeps a security log of all those who visit the crime scene.

Separating the witnesses is the next priority. Witnesses must not be allowed to talk to each other. Crime-scene investigators will compare the witnesses’ accounts of the events. Witnesses are separated so they do not work together to create a story (collusion).

The following questions need to be asked of each witness:

• When did the crime occur?

• Who notified law enforcement?

• Who is the victim?

• Can the perpetrator be identified?

• What did you see happen?

• Where were you when you observed the crime scene?

Scanning the Scene

The forensic crime-scene examiners first need to scan the scene to determine where photos should be taken. A determination may be made of a primary crime scene and secondary crime scene and priorities assigned regarding examination. (The location of the crime is the primary crime scene. If movement to a new location occurs, that location is considered a secondary crime scene.) A robbery in front of a store might be the primary scene, and the home of a suspect might be the secondary scene. A murder may have taken place at one location (primary scene) and the body found at another (secondary scene).

The crime-scene examiner needs to see the scene. Photos of the overall area and close-up photos with and without a measuring ruler should be taken. Triangulation should be included in the photos. Triangulation is a mathematical method of calculating the location of an object from the locations of other objects. Close-ups and photos from varying distances of any evidence and remains should be taken.

A crime-scene investigator eventually makes an accurate sketch of the crime scene, noting the position of the remains (if any) and any other evidence. (You can see a reduced sketch form in Figure 2-3.) All objects should be measured from two immovable landmarks. On the sketch, north should be labeled, and a distance scale should be provided. Any other objects in the vicinity of the crime scene, such as doors, windows, and furniture, should be included in the sketch. If the crime scene is outdoors, the positions of trees, vehicles, hedges, and other structures or objects should be included in the sketch. Later, a more accurate, final copy of the crime scene should be made for possible presentation in court, likely with specialized software.

The type of search pattern varies depending on the size of the area to be searched and the number of investigators. Single investigators might use a gridded, linear, or spiral pattern. A group of investigators might use a linear, zone, or quadrant pattern. These patterns are used systematically, ensuring that no area is left unsearched (Figure 2-4).

Securing and Collecting Evidence

All evidence needs to be properly packaged, sealed, and labeled. Specific procedures and techniques for evidence collection and storage must be followed. Liquids and arson remains are stored in airtight, unbreakable containers. Moist biological evidence is stored in breathable containers so the evidence can dry out, reducing the chance of mold contamination. After the evidence is allowed to air dry, it is packaged in a paper bindle. The bindle (also called a druggist’s fold) can then be placed in a plastic or paper container. This outer container is then sealed with tape and labeled with the signature of the collector written across the tape. An evidence log and a chain of custody document must be attached to the evidence container.

The evidence log should contain all pertinent information, including:

• Case number

• Item inventory number

• Description of the evidence

• Name of suspect

• Name of victim

• Date and time of recovery

• Signature of person recovering the evidence

• Signature of any witnesses present during collection

Packaging Evidence

The paper bindle is ideal packaging for small, dry, trace evidence. The size of the bindle depends on the size of the evidence. If the evidence is small, the bindle can be constructed from a sheet of paper. If the evidence is large, the bindle might be constructed from a large sheet of wrapping paper. The packaging techniques are shown in Figure 2-6 on the next page. The steps are as follows:

1. Choose the appropriate-size sheet of clean paper for the bindle.

2. Crease the paper as shown.

3. Place evidence in the location shown by the X.

4. Fold the left and right sides in.

5. Fold in the top and bottom.

6. Insert the top flap into the bottom flap; then tape the bindle closed.

7. Place the bindle inside a plastic or paper evidence bag. Fold the bag closed.

8. Place a seal over the folded edge of the evidence bag.

9. Have the collector write his or her name over the folded edge.

Material that connects an individual or thing to a certain group. Narrows an identity to a group of persons or things.

Example:

Blood Type

Hair Color

Evidence that identifies a particular person or thing. Narrows an identity to a single person. or thing.

DNA

Hair follicle

Fingerprints

Small but measurable amounts of physical or biological material found at a crime scene.