The Crime Scene

3 methods for crime scene recording: Record The Scene Records of the crime scene in its original state will be used in the subsequent investigation, as well as at trial if necessary. 3 methods for crime scene recording: Photography Sketches Notes Ideally, all three should be used but photography is not always available so sketching and notes should be done at the very minimum.

Photographing the Scene The prerequisite for photographing a crime scene is for it to be unaltered. If objects are moved, positions changed, etc. before the scene is photographed, it must be documented in the notes. At a minimum, 4 types of photographs are required: Overview photograph-shows the entire area and all adjacent areas where important acts occurred before or after the crime. Medium-Range photographs-photographs of objects in relation to the rest of the scene. Close-Up photographs-used to record the details of the object. Close-Up photographs with a scale-a ruler is placed in the photograph to show the relative size of the object.

Sketches Done after the photographs have been taken. 2 Types: Rough Sketch Finished Sketch Sketches should include: All objects that are part of the scene Dimensions of the area and objects of interest A key to show what the objects are A compass Neat and detailed Scaled appropriately

Rough Sketch Finished Sketch

Notes Note taking must be constant and must include: A detailed written description of the scene Location of items of physical evidence recovered Time an item was discovered Who it was discovered by How and by whom it was packaged and marked Who took the item from the scene Remember that this record must be sufficiently detailed because it might be the only source of information for refreshing one’s memory weeks, months or even years down the road. Audio recordings are a faster way to take notes at the scene, however, they have to be transcribed into a written document soon after their recording.

Search methods

Types of Memory

Fingerprinting

No two prints are alike-can be used as identification 3 Principles No two prints are alike-can be used as identification A fingerprint will remain unchanged during an individuals lifetime. Fingerprints can be classified into three ridge patterns.

Types of Prints Visible: prints made after coming into contact with a colored material. Plastic prints: ridge impressions left on a soft surface such as wax. Latent prints: ridge impressions caused by the transfer of sweat and oils on the skin. These must be developed!

Loops: enter, loop around, and exit the same side Ridge Patterns Loops: enter, loop around, and exit the same side Radial and Ulnar Whorl: circle pattern that has one core and one delta Plain whorl, Central Pocket Loop, Double Loop Arch: enter on one side and exit the other side Plain Arch, Tented Arch

Francis Galton: classified prints into loops, whorls, and arches Important People Alphonse Bertillon: first system of classification based off measurements and photographs. Henry Fauld: first person to suggest using fingerprints as identification. Proved in the first court case. Francis Galton: classified prints into loops, whorls, and arches Dr. Juan Vucetich: created the first classification system that allowed prints to be filed and recalled when needed.

AFIS A database of fingerprints used to identify a print To make a match: characteristics must be identical and have the same relative location to one another. Most judicial systems accept between 8 to 16 points to conclude that it’s the same print.

Hair and Fibers

Hair

Used to determine if the hair was pulled out or fell out. Structure 3 Parts: Follicle Used to determine if the hair was pulled out or fell out. Root Shaft: used to determine if the hair is human or animal.

Shaft 3 Layers: Cuticle: outer covering in 3 scale structures: imbricate, spinous, and corona. Cortex: middle layer that includes the pigment molecules Medulla: inner layer that is made up of cells. The medulla is used to determine if the hair is human or animal. If the medulla is greater than 1/3, it is most likely an animal hair.

Fibers

Types of Fibers Natural: plant, animal, and mineral sources. Variation is shape Most common is cotton Synthetic: manufactured from petroleum, coal, or other synthetic chemicals Uniform in shape Most common is polyester

Plain: yarn goes over and under each strand. Weave Patterns Plain: yarn goes over and under each strand. Resembles a checkerboard Twill: one yarn goes over 3 before going under. Creates a stair-step pattern Satin: one yarn goes over 4 or more before going under. Creates a pattern that looks like bricks Knitted: interlocking loops

Can be used to analyze the type of dye and therefore the manufacturer. Chromatography Used to separate dyes Can be used to analyze the type of dye and therefore the manufacturer.

DNA Analysis

Structure of DNA Double Helix made up of nucleotides: Adenine, Thymine, Guanine, and Cytosine Complementary base pairing: A binds to T and C binds to G. Polar: goes from 5’ to 3’ and the opposite direction in the other strand 8% of our genetics code for our traits, the rest are switches, and further instructions Mitochondrial DNA: found in the mitochondria and comes from our mothers. Much more common than nuclear DNA and can be used as an alternative when nuclear DNA cannot be found or there is not enough

Collecting Biological Material Proper Clothing: Latex or Nitrile Gloves Face mask Boot covers Eye protection Lab coat/coveralls Photograph and documentation (sketches and notes) A substrate control: a piece of the material that is close but not part of the biological material being collected. Used for a comparison.

Collecting Biological Material Biological materials should be placed in a paper bag or well ventilated box to discourage the growth of bacteria Dried blood is swabbed with a Qtip that has been dipped in distilled water. The Qtip then goes into a well ventilated box for transport. Soil that contains blood is packaged in an airtight container and immediately frozen. This is to discourage the growth of bacteria that is naturally in the soil.

RFLP

Restriction Fragment Length Polymorphisms 11 Restriction Enzymes are used to “cut” the strand of DNA at a specific nucleotide sequence created fragments of different lengths. We use gel electrophoresis to separate the strands of DNA Fragments travel from the negative to positive electrode Smaller fragments travel farther than large fragments Creates a ladder Original Method of DNA Analysis Requires a large sample of DNA Subject to degredation

PCR and STR’s

PCR-Polymerase Chain Reaction A method of making many copies of a piece of DNA by cycling through heating and cooling to artificially replicate DNA. Strands of DNA are separated Enzymes add nucleotides starting at the primer sequence Makes about 1 Billion Copies in 3 hours

STR-short Tandem Repeats Looking for a repeating sequence of nucleotides at 13 specific locations on both chromosomes. The number of repeats will differ in each individual so we can use them to identify a suspect. The STR’s are separated by length using gel electrophoresis. New Method of DNA Analysis Requires a much smaller DNA sample Is not affected as much by degradation