Chapter 8 - Crime Labs

45 terms by Chemical_plan 

Create a new folder

Advertisement Upgrade to remove ads

Define Forensic Science. What distinguishes it from Criminalistics?

It is that part of science applied to answering legal questions. It is the examination, evaluation, and explanation of physical evidence in law. It encompasses pathology, toxicology, anthropology, Odontology, psychiatry, documents, tool-mark comparison, and many other fields. Criminalistics is only the study of evidence and Forensic Science covers much more than just that.

What difficulties are caused by an investigator not understanding the capabilities and limitations of crime laboratories?

Some investigators are not acquainted with the services a crime lab provides. Some expect too much from the scientific analysis. They expect the lab to provide a solution for every case because of this; some become disappointed and are reluctant to use the services again.

What is the measure of effectiveness of crime laboratories and how do they relate to the 2009 National Academy of Science (NAS) report on forensic science in the United States?

NAS's report found serious deficiencies in the nation's forensic science system and in order to measure the effectiveness of the labs they must have three key items that make them effective: 1. The quality of the lab and its technical capabilities and personnel. 2. The Proximity of the lab. If there is a far distance from a police agency then there is less use of one. 3. The timeliness of the lab. It must be quick to process caseloads of evidence.

What is the most important resource in a crime laboratory?

The most important resource is the scientific staff.

How important is DNA analysis in a criminal investigation?

It is very important because it has a unique code for every person (except twins) and it allows to place a suspect at the scene of the crime. Although the effectiveness of DNA depends on the ability of a witness to explain the probability that no other person, except an identical twin, has the same DNA type.

What are AFIS, NIBIN, IAFIS, and CODIS?

AFIS is the Automated Fingerprint Identification System that can scan and digitize fingerprints by reading spacing and ridge patterns and translating them to computer code. NIBIN is the National Integrated Ballistic Information Network this network compares images of ballistic evidence, both projectile and casings obtained at crime scenes. IAFIS is the Integrated Automated Fingerprint Identification System is a database run by the FBI, which contains fingerprints from criminals, military personnel, federal employees, and volunteers. CODIS is the Combined DNA Index System which contains a collection of DNA specimens from all convicted offenders.

What are the main areas of responsibility of the ATF laboratories?

They maintain five forensic science laboratories. In addition to analyzing alcohol and tobacco samples, conduct forensic examinations in support of the bureau's explosives, bombing and arson, and illegal-firearms-trafficking investigations.

What limitations are placed on the submission of evidence to the FBI laboratory?

If any evidence in the case has been or will be subjected to the same type of technical examination by another lab or other experts. It also does not accept cases from other crime labs that have the capabilities of conducting the requested examination. They also no longer accept evidence from state and local law-enforcement agencies regarding property crime investigations unless the case involves personal injury or the offenses were designed to cause personal injury

What are the primary DNA analysis techniques that have been used since 1985?

There are two techniques: One requires larges amounts of the sample and the manual technique is called Restriction Fragment Length Polymorphism (RFLP). The system is slow but produces good results. Technological advances have sped up the process and require little amounts of the sample. This is called Polymerase Chain reaction (PCR).

Distinguish the Frye test from the Daubert test regarding the admissibility of scientific evidence. What is the importance of these two cases?

The Frye test is a technique that is applied to evidence, it must be sufficiently established to have gained general acceptance in its particular field. This makes evidence admissible in court. The Daubert test requires evidence to only be admissible by following the five rules. The judge acts as the gatekeeper and determines if the evidence is admissible. Rules are: 1. Whether the theory can be tested, it has been subjected to peer review and publication, its known or potential error rate, existence and maintenance of standards controlling its operation, and widespread acceptance within the relevant scientific community.

What are some of the major problems confronting police crime labs?

Lack of training, lack of accreditation, DNA contamination, sentencing mistakes and poor training, backlog of cases, scandals and mistakes within the FBI crime lab.

What is a nonfelonious homicide? What are the two types of nonfelonious homicide and briefly describe

May be justifiable or excusable
There are two type of nonfelonious homicide:
Justifiable homicide is the necessary killing of another person in performance of a legal duty or the exercise of a legal right when the slayer was not at fault.
Excusable homicide differs from justifiable homicide in that one who commits an excusable homicide is to some degree at fault but the degree of fault is not enough to constitute a criminal homicide

What is a felonious homicide? What are the two categories of felonious homicide and briefly describe

Typically fall into one or two categories: Murder and manslaughter
Murder is the killing of any human being by another with malice aforethought
Manslaughter is a criminal homicide that is committed under circumstances not severe enough to constitute murder but cannot be classified as either justifiable or excusable homicide.

What is the definition of "chain-of-custody"

Chain of custody is the witnessed, unbroken, written chronological record of everyone who had an item of evidence, and when each person had it; also accounts for any changes in the evidence.

What is the timeframe for a "chain-of-custody?" When does it begin and end?

The timeframe is the entirety of the life of that item of evidence. It begins the moment the evidence is collected (seized) and ends at adjudication.

What is a forensic pathologist? What types of examinations do they perform?

A forensic pathologist, a subspecialty of pathology, studies how and why people die. They perform autopsies in order to determine cause and manners of death.

What are the five manners of death?

Homicide, suicide, accidental, unexplained and natural

7. What is an example of a cause of death?

Blunt force trauma, strangulation, drowning, gunshot wound

What is the postmortem interval?

It is the interval between the time of death and the time that the body is found.

What are five (5) types of observations that when used together, provide the best estimate of the time of death?

- Body temperature
- Rigor mortis
- Livor mortis
- Decompositional changes
- Stomach contents

What is algor mortis?

- Algor mortis is a decrease in body temperature
- After death, the body cools from its normal internal temperature of 98.6 degrees to the surrounding environmental temperature.

What factors affect the rate of cooling of a deceased individual?

• The size of the body
- The heavier the physique and the greater the obesity, the slower the heat loss
• Clothing and coverings
- Insulate the body from the environment and therefore cooling is slower
• Movement and humidity of the air
- Cooling is said to be more rapid in a humid rather than a dry atmosphere, because moist air is a better conductor of heat
• Immersion in water
- A cadaver cools more rapidly in water than in air, because water is a far better conductor of heat.

What is rigor mortis?

The freezing (locking) and increasing rigidity of the joints.

What are two factors that affect rigor mortis?

Body temperature and metabolic rate.

What is livor mortis?

- Is the reddish purple coloration in dependent areas of the body due to accumulation of blood in the small vessels of the dependent areas secondary to gravity.

What are three reasons livor mortis may be important?

• it may help estimate the time of death
• It may indicate that the body has been moved after death.
• It may indicate the cause of death

What is a cadaveric spasm?

- Refers to a kind of instant rigor mortis, except that is occurs at a more accelerated rate.
- Also commonly called "a death grip."

Describe the process of decomposition.

- As rigor passes, skin first turns green at the abdomen
- As discoloration spreads to the rest of the trunk, the body begins to swell because of bacterial methane-gas formation.
- When a body is bloated, epidermal sloughing and hemoglobin degradation begin.
- As bloating continues, air is forced from the skin. The increased internal pressure, caused by bacterial gas production, forces decomposed blood and body fluids out of body orifices by a process called purging.

What is forensic entomology?

Forensic entomology is the study of insects associated with a dead body, which is used to determine the elapsed time since death.

19. What are not considered insects?

• Spiders, scorpions, ticks, mites, millipedes, centipedes

What are the two ways to use insects to determine the time since death?

- Dipteran larval development and insect succession over time.

21. What is dipteran larval development?

• Used in the first hours, days or weeks after death
• Can be used to determine the time of death accurate to a day or less, or a range of days.
• Insects used in this method are the first to arrive on the corpse, the blow fly. These flies are attracted to the corpse very soon after death.
• They lay their eggs on the corpse, usually in a wound, if present, or in any of the natural orifices.
• Their development follows a set, predictable cycle, and each of these developmental stages takes a set, known time.

22. What is insect succession over time?

- Based on the fact that the human corpse, or any kind of carrion, supports a rapidly changing ecosystem. The body decomposes from a fresh state to dry bones in a matter of weeks or months depending on the geographic region.
- As the body decomposes, it goes through a predictable sequence of biological, chemical, and physical changes.
• Each of these changes is attractive to a different group of insects.

What two types of insect colonize a body?

Species of flies (diptera) and beetles (coleoptera)

What are the five most common types of wounds encountered by police officers in injury and death investigations?

- Firearm wounds
- Incised wounds
- Stab wounds
- Puncture wounds
- Lacerations

25. In reference to gunshot wounds, describe a contact wound, a close shot and a distant shot.

Contact wounds
• Made when the muzzle of the weapon is pressed against the body when the shot is fired.
• Soot, metallic particles, and powder residues are driven into the body and can be found there during the autopsy.
Close shot wounds
Produces a zone of blackening around the entrance wound of the track, either on the skin or clothes.
• In a close shot, a considerable amount of incompletely burned powder residue is found on the target.
• Close shots with black powder show marks of burning up to a distance of 4 to 6 inches and a distinct deposit of powder smoke up to 10 to 12 inches.
Distant shot wounds
• A shot fired at a distance greater than 18 inches (approximately 3 - 5 feet)
• Not likely to see much except for the wound; however very dependent on the gun and ammunition involved.

26. What is GSR?

Gunshot residue which is made up of three elements: lead, barium and antimony. It is expelled from the barrel and other openings of a firearm in a cone-like fashion with the heavier material traveling farther than the lighter materials.

27. What is an incised wound?

- More commonly referred to as a "cutting wound"
- Inflicted by a sharp-edged instrument such as a knife or razor.
- LONGER THAN IT IS DEEP due to swipe action

What is a stab wound?

A stab wound is inflicted by an object (does not necessarily have to be sharp) penetrating into the skin. Stab wounds are DEEPER THAN THEY ARE LONG.

29. What is a laceration?

• Lacerations are open, irregular shaped wounds caused by blunt objects such as clubs, pipes, pistols.
• Bleed freely and are characteristically accompanied by bruising around the edges.

30. What are defensive wounds?

• Are suffered by victims attempting to protect themselves from an assault, often by a knife or club.
• These wounds are commonly found on the palms of the hands, the fingers, and the forearms.

31. What are two types of strangulations?

Ligature and manual strangulations.

32. What are some of the methods most commonly employed in suicides?

- Shooting
- Hanging
- Ingesting sleeping pills
- Drowning
- Cutting and piercing
- Ingestion of poisons
- Inhaling gases
- Jumping from high places
- Intentionally crashing a vehicle

33. What is the most frequently encountered gas in medico-legal death investigations?

Carbon monoxide

34. What are the three types/degrees of burns and describe.

1st degree
• Usually limited to redness with minor pain at the site of injury
• Only involves the epidermis
• Ex: sunburn

2nd degree
• Redness with superficial blistering
• Can involve more or less pain depending on the level of nerve involvement
• Involves the superficial dermis and may involve the deep dermis layer

3rd degree
• Occurs when the epidermis is lost with damage to the subcutaneous tissue
• Exhibits charring and extreme damage of the epidermis
• Usually whitish in appearance and results in heavy scarring
• May require grafting
• Not painful, because nerves are damaged; however, these burns are surrounded by first and second-degree burns, which are painful

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set