Forensics CH3 Physical Evidence

Types of Physical Evidence (20 listed):

•Blood, semen, and saliva. •Documents. •Drugs. •Explosives. •Fibers. •Fingerprints. •Firearms and ammunition. •Glass. •Hair. •Impressions. •Organs and physiological fluids. •Paint. •Petroleum products. •Plastic bags. •Plastic, rubber, and other polymers. •Powder residues. •Soil and minerals. •Tool marks. •Vehicle lights. •Wood and other vegetative matter.

The Locard's Exchange Principle states that "_____." For example, burglars will leave traces of their presence behind and will also take traces with them. They may leave hairs from their body or fibers from their clothing behind and they may take carpet fibers away with them.

"With contact between two items, there will be an exchange."

Individual Characteristics: Class Characteristics:

-Evidence that can be associated to a common source with an extremely high degree of probability is said to possess individual characteristics. -Evidence associated only with a group is said to have class characteristics.

Examiners will analyze _____ or other _____ to find clues to link it to a crime scene or a specific suspect. They will analyze: Other unique features, such as _____ or _____, may provide useful clues.

A ransom note or other documents. The type of paper used, printing method or handwriting style, and type of ink. Watermarks on stationary or indentations made as someone wrote on a page in a notebook.

Forensic anthropologists analyze skeletal remains to determine four characteristics for a victim: 1) _____ - Determined by examining the pelvis, humerus, and femur 2) _____ - Determined by analyzing the development of the teeth, bone growth, and the length of specific bones, such as the femur. 3) _____ - Determined by analyzing the skull for characteristics that are common among people of different _____. DNA samples can be collected from _____, _____, and _____ to provide clues to a person's identity. Scientists may also be able to gain clues as to a person's _____, or the cause of death based on _____ and other signs of _____.

Age, sex, race, and stature (height/build). 1) Sex 2) Age and stature 3) Race Bone, teeth, and hair. Past/recent injuries, bone fractures and trauma.

The crime laboratory is frequently requested to identify the chemical composition of _____. •It may be asked to identify _____ in residues recovered from the debris of a fire, or it may have to identify the nature of _____ residues—for example, dynamite or TNT. •The identification of _____, _____, _____, or _____ are also very common and as a matter of routine, include a determination for species origin.

An illicit drug. Gasoline, explosive. Blood, semen, hair, or wood.

There are 3 types of fingerprint patterns: _____, _____, and _____. Investigators also identify unique _____ characteristics in a fingerprint that can be used to identify a suspect or victim. _____ is a database used by investigators at local, state, and national levels to search for matches to fingerprints found at a crime scene.

Arches, loops, and whorls. Ridge. AFIS (Automated Fingerprint Identification System).

Physical and chemical analysis of paint evidence (chips or residue) can indicate it's class, such as _____, _____, _____, etc. The evidence can be compared to 40,000 different types of paint classified in a database, which can be used to identify _____ or _____. Paint evidence can also indicate individual characteristics if an investigator is able to find similarities between two samples, such as:

Automobile paint, house paint, nail polish. A particular make or model of car or brand of tool. The color, number of layers, chemical composition, or a physical match between the edges of two paint chips - one from a tool and one from a crime scene.

_____, _____, _____, _____, and _____ can be analyzed to give investigators information about the crime as well as its victim or the suspect. Chemicals and _____ light can be used at a crime scene to find body fluid evidence. Areas with potential evidence are _____, _____ and _____, which are air tight and have a low risk of cross contamination.

Blood, semen, saliva, sweat, and urine. Ultra violet. Swabbed, bagged and collected in vials.

Glass particles can be found at various crime scenes, such as: Glass at a crime scene is analyzed to determine its: (The results of the tests provide clues about the crime and help investigators connect the evidence to a suspect or other object used in a crime, such as matching glass from a crime scene to a headlight to a suspect's car.)

Breaking and entering, hit and run, vandalism, or murder. Color, surface characteristics, tint, thickness, density, chemical composition, and refractive index (RI).

When an object is _____, _____, or _____, two unique edges are formed, which are referred to as _____ lines. These edges can be compared by the naked eye or with microscopes to see if they fit together , which indicates that they may have been: Investigators may compare the edges on pieces of _____, _____, _____, _____, _____, etc. to find possible matches.

Broken, torn, or cut. Fracture. Part of the same object at one time. Tape, glass fragments, paint chips, pieces of a car from an accident, paper bag.

Investigators can extract DNA from almost any tissue, including: (The DNA is used to create a profile that can be compared to profiles from suspects or victims.) _____ is a database maintained by the FBI that is used to find matches to unknown DNA samples from a crime scene.

Hair, fingernails, bones, teeth and body fluids. CODIS (Combined DNA Index System).

_____ and _____ may be transferred from the suspect or the suspect's clothes to the victims' and vice versa. For example, a suspect may pick up _____ on his shoes or leave _____ behind at a crime scene. _____ can be examined to identify their origin, such as human or animal. _____ with roots intact can be tested for DNA. _____ are used to make clothing, carpeting, furniture, beds, and blankets. They may be natural _____ from plants or animals or synthetic _____ that are man-made.

Hairs and Fibers. Carpet fibers, Hairs. Hairs. Fibers.

The examination of physical evidence by a forensic scientist is usually undertaken for _____ or _____ purposes. _____ has as its purpose the determination of the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. A _____ analysis subjects a suspect specimen and a standard/reference specimen to the same tests and examinations for the ultimate purpose of determining whether or not they have a common origin.

Identification or Comparison. Identification. Comparison.

In all cases, it is not possible to state with mathematical exactness the probability that the specimens are of common origin. It can only be concluded that this probability is so high as to defy mathematical calculations or human comprehension. (Which characteristic is this?)

Individual.

•Examples (Which characteristic do these define?): -The matching ridge characteristics of two fingerprints -The comparison of random striation markings on bullets or tool marks -The comparison of irregular and random wear patterns in tire or footwear impressions -The comparison of handwriting characteristics -The fitting together of the irregular edges of broken objects in the manner of a jigsaw puzzle -Matching sequentially made plastic bags by striation marks running across the bags

Individual.

Explosive substances can be examined to determine: Traces of explosives found on _____, _____, _____, or _____ that may be matched to explosives from the crime scene. (Materials used to make an explosive device will be compared to evidence found in the suspect's possession to confirm a match.)

Its chemical composition to identify the type of explosive used and its origin. A suspect's clothing, skin, hair, or other objects.

Impression evidence can be _____, _____, or _____ to compare to a suspect's shoes or tires. Investigators will examine the evidence to identify the _____ or _____ and other physical features to provide leads in the case. Shoes and tires will also show wear patterns after being used for a period of time as well as other features (_____, _____, and _____) that can be used to match evidence to specific items. (For example, shoeprints can be matched to a suspect based on how the treads on the shoes that are worn down due to that person's walking style.)

Photographed, lifted with tape, or cast with plaster. Brand of shoe or tire based on its tread pattern. Scratches, nicks, and cuts.

It would be impossible to list all the objects that could conceivably be of importance to a crime. Almost anything can be _____. Although you cannot rely on a list of categories, it is useful to discuss some of the most common types of _____. The purpose of recognizing _____ is so that it can be collected and analyzed. It is difficult to ascertain the weight a given piece of _____ will have in a case as ultimately the weight will be decided by a jury.

Physical evidence.

To comprehend the evidential value of a comparison, one must appreciate the role that _____ has in ascertaining the origins of two or more specimens. •Simply defined, _____ is the frequency of occurrence of an event. •In flipping a coin, _____ is easy to establish. •With many analytical processes exact _____ is impossible to define.

Probability.

•The method used to support a likely sequence of events by the observation and evaluation of physical evidence, as well as statements made by those involved with the incident, is referred to as: •Crime-scene _____ relies on the combined efforts of medical examiners, criminalists, and law enforcement personnel to recover physical evidence and to sort out the events surrounding the occurrence of a crime. •The physical evidence left behind at a crime scene plays a crucial role in _____ the events that took place surrounding the crime. •Although the evidence alone does not describe everything that happened, it can support or contradict accounts given by witnesses and/or suspects. •Information obtained from physical evidence can also generate leads and confirm the _____ of a crime to a jury. •The collection and documentation of physical evidence is the foundation of a _____.

Reconstruction.

A comparative analysis has the important role of determining whether or not a _____ and a _____ have a common origin. •Both the _____ and the _____ are subject to the same tests. •The forensic comparison is actually a two-step procedure. -First: -Second:

Suspect specimen and a standard/reference specimen. Standard/reference and the suspect specimen. Combinations of select properties are chosen from the suspect and the standard/reference specimen for comparison. Once the examination has been completed, the forensic scientist must be prepared to render a conclusion with respect to the origins.

The object of an identification is to determine the physical or chemical identity with as near absolute certainty as existing analytical techniques will permit. -The process of identification first requires: -Once these test results have been established, they may be: -Second, identification requires:

The adoption of testing procedures that give characteristic results for specific standard materials. Permanently recorded and used repeatedly to prove the identity of suspect materials. That the number and type of tests needed to identify a substance be sufficient to exclude all other substances.

•As the number of different objects linking an individual to a crime scene increases, so does: •Just as important, a person may be _____ or _____ from suspicion if physical evidence collected at a crime scene is found to be _____ from standard/reference samples collected from that subject.

The likelihood of that individual's involvement with the crime. Exonerated or excluded. Different.

_____ and _____ form on the edges of a tool as it is used, which can be used to identify matches between evidence and suspects. Tools may also pick up _____ or _____ that can be tested or have _____ that can be lifted.

Tiny nicks and chips. Traces of blood or other substances, fingerprints.

Body Fluid Examples:

Vomit and urine can be used to test for alcohol, drugs, and poisons. 1) Cigarette butts may contain dried saliva. 2) Semen containing sperm is valuable for DNA analysis. 3) Blood can provide DNA evidence and blood spatter can provide clues about the crime.

_____ can often be matched to weapons or tool marks on the weapon. Investigators may also be able to determine the weapon's _____, _____, and _____. Analysis of a _____ may provide clues to:

Wounds. Size, shape and length. Wound. A victim's injuries, characteristics of the suspect (left-handed, right-handed, height, etc.), and positions of the victim and suspect at the time of the incident.

_____, _____, or _____ evidence can reveal where a person has traveled and may be picked up at a crime scene or left behind. Investigators examine the samples for _____, _____, _____, and other _____ to find links to a specific crime scene.

Dust, dirt, or sand. Chemical composition, pollen, plant material, and other organic matter.

The value of trace (or contact) forensic evidence was first recognized by _____ in 1910. He was the director of the very first crime laboratory in existence, located in Lyon, France.

Edmund Locard.

_____, _____, and other _____ can provide useful clues about a corpse. Forensic _____ use factors such as _____, _____, and their knowledge of _____ to help them estimate the _____ (the time between death and the discovery of the body).

Flies, beetles, and other insects. Entomologists. Weather conditions, the location and condition of the body, and their knowledge of the life cycles of insects, postmortem interval or PMI.

Characteristics of ammunition, firearms, and residue are examined to find matches between suspects and the evidence found at a crime scene. Chemical tests can reveal _____ on the _____, _____, or _____ of a victim or suspect to indicate how close a person was to a fired gun. Rifling (grooves) in a gun barrel causes _____, _____ and _____ upon fired bullets, which can be matched to the weapon that fired them. Police are able to search the _____ database to compare markings from _____, _____, and _____ to ballistic evidence.

Gunshot residue (GSR) on the hands, face, or clothing. Distinctive grooves, indentations and scratches. Integrated Ballistics Identification System (IBIS), bullets, cartridge cases and shotgun shells.

•Surprising to the inexperienced forensic scientist is the frequent inability of the laboratory to relate physical evidence to a common origin with a high degree of certainty. •Evidence is said to possess _____ characteristics when it can be associated only with a group and never with a single source. •Here again, probability is a determining factor. •Nevertheless, the high diversity of _____ evidence in our environment makes their comparison very significant in the context of a criminal investigation. •One of the current weaknesses of forensic science is the inability of the examiner to assign exact or even approximate probability values to the comparison of most _____ evidence. •For example, what is the probability that a nylon fiber originated from a particular sweater, or that a paint chip came from a suspect car in a hit and run? •There are very few statistical data available from which to derive this information, and in a mass-produced world, gathering this kind of data is increasingly elusive. •One of the primary endeavors of forensic scientists must be to create and update statistical databases for evaluating the significance of _____ evidence. •Most items of _____ evidence retrieved at crime scenes cannot be linked definitively to a single person or object. •The value of _____ evidence lies in its ability to provide corroboration of events with data that are, as nearly as possible, free of human error and bias. •The chances are low of encountering two indistinguishable items of _____ evidence at a crime scene that actually originated from different sources. •When one is dealing with more than one type of _____ evidence, their collective presence may lead to an extremely high certainty that they originated from the same source. •Finally, the contribution of _____ evidence is ultimately determined in the courtroom. (Which characteristic is this?)

Class/Class physical.