Forensic Notes

Sketching the Scene -

1. North should be labeled and a scale of distance should be included, 2. all important objects (weapon and body) should be measured from two immovable landmarks, 3. any other objects in the vicinity of the crime scene should be included in the sketch, and 4. also include: date, time, location, case number, and names ( sketched by and verified by).

Securing and Collecting the Evidence -

all evidence must be properly packaged, sealed and labeled using specific techniques and procedures.

Crime Scene Reconstruction -

allows the detectives to form a hypothesis of the sequence of events from before the crime was committed through it's commission.

Secondary Crime Scene -

an alternate location where additional evidence may be found.

Biology/DNA -

analysis of body fluids and dried stains such as blood, semen, and saliva.

Crime Scene -

any physical location in which a crime has occurred or is suspected of having occurred.

Legal Considerations -

any removal of evidence from a crime scene must be in accordance with the fourth Amendment.

Police Officers -

are typically the first to arrive at the a crime scene. They are responsible for securing the scene so no evidence is destroyed and detaining persons of interest in the crime.

Biological Evidence -

body or body parts, body fluids, hair, leaves or other plant parts, natural fibers, feathers, and wood.

Drug Chemistry -

determines the presence of controlled substances and the identification of marijuana.

The CSI Unit -

documents the crime scene in detail and collects any physical evidence.

Questioned Documents -

examination of documents to compare handwriting, ink, paper, writing instruments, printers, and other characteristics that would help to identify it's origin.

Toolmarks -

examines marks left by tools on objects at a crime scene or on a victim, such as a hammer used to break a door or a screwdriver used to pick a lock.

Direct Evidence -

first hand observations (eyewitness account, videos, and confessions).

Scan the Scene -

forensic examiners scan the scene to see where photos should be taken. The primary and secondary crime scenes must be determined.

Fiber Evidence -

is the smallest unit of a textile material that has a length many times greater that it's diameter. A fiber can be spun with other fibers to form a yarn that can be woven or knitted to form a fabric. The type and length of fiber used, the type of spinning method, and the type of fabric construction all affect the transfer of fibers and the significance of fiber associations. This becomes very important when there is a possibility of fiber transfer between a suspect and a victim during the commission of a crime. Matching unique fibers on the clothing of a victim to fibers on a suspect's clothing can be very helpful to an investigation, whereas the matching of common fibers such as white cotton or blue denim fibers would be less helpful. The discovery of cross transfer and multiply fiber transfer between the suspect's clothing and the victims clothing dramatically increases the likelihood that these two individuals has physical contact.

Evidence Log -

includes description of evidence, name of suspect, name of victim, date and time of recovery, signature of person recovering the evidence, and signature of witness present during collection.

Testimonial (direct) Evidence -

includes oral or written statements given to police as well as court testimony by people who witnessed an event.

Circumstantial Evidence -

indirect evidence that can be used to imply a fact but does not directly prove it.

Detectives -

interview witnesses and consult with the CSI Unit. They investigate the crime by following leads provided by witnesses and physical evidence.

District Attorney -

is often present to help determine if any search warrants are required to proceed and obtains those warrants from a judge.

Natural Fibers -

many different natural fibers that come from plants and animals are used in the production of fabric. Cotton fibers are the plant fibers most commonly used in textile materials. The animal fiber most frequently used in the production of textile material is wool, and the most commonly used wool fibers originated from sheep.

Specialists (forensic entomologists, anthropologists, or psychologists) -

may be called in if the evidence requires expert analysis.

Medical Examiner (if homicide) -

may or may not be present to determine a preliminary cause of death.

Medulla -

may vary in thickness, continuity, and opacity. It may also be present in some species. Like the cuticle, the medulla can be important for distinguishing hairs of different species, but often does not lend much important information to the differentiation between hairs from different people.

Microscopy -

microscopic identification and comparison of evidence such as hair, fibers, woods, soils, building materials, insulation and other materials.

Synthetic Fibers -

more than half of all fibers used in the production of textile materials are synthetic or man-made. Nylon, rayon, and polyester are all examples of synthetic fibers.

Druggist's fold for Evidence -

most biological evidence is stored in breathable containers so the evidence can dry out, reducing the chances of mold contamination. After the evidence has air dried, it is packaged into a paper bindle (or druggist's fold) then placed in a paper or plastic container.

Individual Evidence -

narrows evidence down to a single person or thing.

Class Evidence -

narrows evidence to a group of persons or things.

See the Scene -

a crime scene examiner looks at the scene. The Photography Unit takes photos of the overall area and close up photos with and without a measuring ruler.

Analyze the Evidence -

a forensic lab processes all evidence the crime scene investigation team collected.

Chain of Custody -

a list of all persons who came into possession of an item of evidence.

Search for Evidence -

a pattern should be walked and location of evidence marked, photographed and sketched.

Biology of Hair -

hair is composed of the protein Keratin, which is also the primary component of finger and toe nails. Hair is produced from a structure called the hair follicle. Humans develop hair follicle during fetal development, and no new follicles are produced after birth. Hair color is mostly the result of pigments, which are chemical compounds that reflect certain wavelengths of visible light. Hair shape (round or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearance of hair can be affected by nutritional status and intentional alteration (heat curling, perms, straightening, etc). The body area (head, arm, leg, back, etc) from which hair originated can be determined by the sample's length, shape, size, color, and other physical characteristic. In order to test hair evidence for DNA, the root must be present.

Hair Structure -

hair is composed of three principal parts: cuticle- outer coating composed of overlapping scales, cortex- protein-rich structure around the medulla that contains pigment, and the medulla- central core (may be present). The structure of hair has been compared to that of pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside.

Latent Prints -

identification and comparison of fingerprints or other hidden impressions from sources like feet, shoes, ears, lips or the tread on vehicle tires.

Trace Chemistry -

identification and comparison of materials from fires, explosives, paints, and glass.

Accomplice -

person associated with someone suspected of committing a crime.

Suspect -

person thought to be capable of committing a crime.

Physical Evidence -

refers to any material items that would be present at the crime scene, on the victims, or found in a suspect's possession.

Trace Evidence -

refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or ski cells.

Control Sample -

should be taken from the victim for purposes of exclusion (blood, hair, etc).

ALIBI -

statement of where a suspect was at the time of the crime.

Ballistics (firearms) -

study of bullets and ammunition through the comparison of fired bullets, cartridges, guns, gunpowder patterns on people and objects.

Toxicology -

tests body fluids and tissues to determine the presence of drugs and poisons.

Securing the Scene -

the first responding police officer must make sure the scene is secure by first making sure all individuals in the area are safe and second by preserving evidence.

Step 1 : Interview -

the first step in investigating a crime scene is to interview the first officer at the scene or the victim to determine what allegedly happened, what crime took place and how was the crime committed. This information may not be factual information but it will give the investigators a place to start.

Primary (preliminary) Crime Scene -

the original location of a crime or accident.

Step 2 : Examine -

the second step in the investigation of a crime scene, which will help identify possible evidence, identify the point of entry and point of exit, and outline the general layout of the crime scene.

Step 3 : Document -

the third step in the protocol involves creating a pictorial record of the scene as well as a rough sketch to demonstrate the layout of the crime scene and to identify the exact position of the deceased victim or other evidence within the crime scene.

Step 4 : Process -

this is the last step in the protocol. The crime scene technician will process the crime scene for evidence, both physical and testimonial evidence. IT is the crime scene technicians responsibility to identify, evaluate and collect physical from the crime scene for further analysis by a crime laboratory.

Cuticle -

varies in it's scales, thickness, and whether or not it contains pigment. Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people.

Cortex -

varies in it's thickness, texture, and color. Distribution of the cortex is perhaps the most important component in determining from which individual a human hair my have come. Microscopic examination can also reveal the condition and shape of the root and tip.

The Locard Exchange -

whenever two objects come in contact with one another, a cross-transfer of physical evidence can occur

Separating the Witnesses -

witnesses must not be allowed to talk to one another. This prevents them from working together to create a story.