4 Circumstantial Evidence

Introduction Direct evidence involves eyewitnesses who have through one or more of their five senses, experienced something relative to the crime in question. Circumstantial evidence is evidence from which an inference can be drawn and which includes items such as physical evidence.

Class and Individual Evidence Two broad categories of physical evidence Class evidence Cannot be linked to a particular person or an object but only to a class of objects May acquire individual characteristics over time Individual evidence Can be linked to a person or a specific object

Weapons Ballistics Interior ballistics Exterior ballistics The identification of firearms, bullets, cartridges, and shotgun shells Interior ballistics Refers to the functioning of firearms through the firing cycle Exterior ballistics The study of projectiles in flight continued on next slide

Weapons Primary sources for weapon identification The inside barrel The firing pin The breech face in which the firing pin is located The chamber The ejector The extractor continued on next slide

Weapons Describe the firearm by: Collect Manufacturer Serial number Caliber Collect Cartridge cases Spent bullets continued on next slide

Weapons Gunshot residue examination May indicate if a person has recently fired a weapon through skin analysis

Blood Hydrodynamics of blood drops Indicates the distance of the fall Indicates the direction of movement May help to narrow the size of the suspect group Support the identity of the suspect when located. Plot the movements of the victim and suspect. continued on next slide

Blood Kastle-Meyer color test determines if the stain is blood. Luminol tests for blood that has been cleaned up by reacting with trace residue of blood and producing a blue glow in a darkened area. Can detect bloodstains diluted up to 100,000 times continued on next slide

Blood Precipitin tests determine if the blood is human or animal. Gel diffusion also tests if the blood is human or animal.

Imprints and Impressions Marks left on the surface by protruding parts of a person or vehicle May include a bloody handprint, or tire tread marks Impressions Made by a person or object in material softer than the item of evidence May include tire tracks or footprints continued on next slide

Imprints and Impressions Fingerprints may be found as either imprints or impressions. Contaminated prints are bloody prints left on weapons or left at the scene. Plastic prints are prints left in soft material.

Latent Prints Usually cannot be seen with the naked eye and must be developed Smooth, nonporous surfaces may be dusted with powder. Porous surfaces, like paper, use iodine fuming or ninhydrin process. Smooth, slippery surfaces use cyanoacrylate fuming process.

Fingerprints 55 million sets of fingerprints are maintained on the FBI database known as Automated Fingerprint Identification System (AFIS).

Tool Marks Likely to be found at the scene of burglaries of other crimes involving a forced entry It is important to locate the impression at the scene and to record the general description and measurements. Photographs and measurements of the tool marks become evidence.

Trace Evidence: Hair Hair can be transferred between individuals and objects during a crime. It is typically transferred during the commission of personal crimes. If the root bulb is attached, DNA analysis can be performed. continued on next slide

Trace Evidence: Hair Without DNA analysis, the crime laboratory would conduct a microscopic analysis of the hair to determine: Origin Racial origin Age and sex Forcible removal Hair comparison

Trace Evidence: Fibers Fibers are key items of evidence in personal crimes such as homicides, physical assaults, and sexual assaults where cross-transfer of fibers may occur between the clothing of the suspect and the victim. continued on next slide

Trace Evidence: Fibers Laboratory analysis includes the following: Torn clothing Microscopic examination Analytical techniques continued on next slide

Trace Evidence: Glass Glass is important in hit-and-run investigations, burglaries, and assault cases when the victim is struck with an instrument such as glass bottle. Radial fractures Concentric fractures Fracture match Links the suspect to the crime as only one piece of glass will fill the void

Trace Evidence: Paint Paint is usually found in the form of smears or chips. Lacquer, enamel, and varnish can be identified by physical and chemical properties. With automobile paints, it is possible to determine the type of vehicle.

Trace Evidence: Questioned Documents Questioned documents may include checks, suicide notes, and charred papers. The general style of a typewritten document, margins, separation of words, spelling errors, and paragraphing contribute to the identification of the person who typed it. continued on next slide

Trace Evidence: Questioned Documents Indented or embossed writing is sometimes found on telephone pads, and other impressionable surfaces.