forensics

How does the textbook define forensic science?

Forensic science is the application of science to criminal and civil laws that are enforced by police agencies in a criminal justice system.

Why is Mathieu Orfila considered "the father of forensic toxicology"?

Orfila published the first scientific treatise on the detection of poisons and their effects on animals.

What was Francis Galton's principal contribution to forensic science?

Galton undertook the first definitive study of fingerprints and developed a methodology of classifying them for filing.

How did Calvin Goddard advance the science of firearms examination?

Goddard was the first to use a comparison microscope to analyze bullets to determine whether they were fired from the same gun.

What is Locard's exchange principle?

Locard's exchange principle states that whenever two objects come into contact with one another, there is exchange of materials between them. When this happens during the commission of a crime, the cross-transfer of evidence can connect the suspect to his or her victim.

What major advance in forensic science did the state of California undertake in 1972?

In 1972 California began creating an integrated network of state-operated forensic laboratories consisting of regional and satellite facilities

How does the British system of forensic laboratories differ from that of the United States?

In contrast to the American system of independent government laboratories, Britain and Wales have privatized their forensic science services.

How has the emergence of the "fee-for-service" system affected the practice of forensic science in Great Britain?

The fee-for-service concept has encouraged the creation of a number of private laboratories that make their services available to police and defense alike

List three reasons for the unparalleled growth of crime laboratories in the United States since the 1960s.

First, Supreme Court decisions in the 1960s required police to place greater emphasis on securing scientifically evaluated evidence and all but eliminated confessions as a routine investigative tool. Second, the dramatic increase in U.S. crime rates led to a greater need for scientific examination of criminal evidence. Third, the advent of DNA profiling led to a need for crime labs to expand their staffs and modernize their facilities to meet the demands of DNA technology.

Describe how the structure of the U.S. federal government has affected the organization of crime labs in the United States.

The federal system of government emphasizes the importance of retaining local control over important matters such as criminal prosecution. This has led to the growth of many local and state crime laboratories and precluded the creation of a national system. In addition, the federal government has no single law enforcement or investigative agency that has unlimited jurisdiction throughout the country.

List three main reasons for the wide variation in total services offered by crime labs in different communities.

Three main reasons for the wide variation in total services offered by crime labs are variations in local laws, different capabilities and functions of the organization to which a laboratory is attached, and budgetary and staffing limitations.

Describe the basic duties of the physical science unit in a crime lab and give three examples of the type of work performed by a physical science unit.

The physical science unit applies principles and techniques of chemistry, physics, and geology to the identification and comparison of crime scene evidence. Three examples of the type of work performed by the physical science unit are drug identification, soil and mineral analysis, and examination of trace physical evidence.

In addition to the physical science unit, what four units typically are found in full-service crime labs? List at least one function performed by each of these units.

The biology unit performs DNA profiling of dried bloodstains and other body fluids, compares hairs and fibers, and identifies and compares botanical materials such as wood and plants. The firearms unit examines firearms and ammunition of all types, examines garments and other objects in order to detect firearms discharge residues, and examines crime scene evidence to approximate the distance from a target at which a weapon was fired. The document examination unit studies questioned documents to ascertain their authenticity and/or source; analyzes paper and ink; and examines indented writings, obliterations, erasures, and burned or charred documents. The photography unit examines and records physical evidence, uses specialized photographic techniques to make invisible information visible to the naked eye, and helps prepare photographic exhibits for courtroom presentation.

List two optional units found in most crime labs and give at least one example of the type of work done by each.

The toxicology unit examines body fluids and organs to determine the presence or absence of drugs and poisons, determines the alcoholic consumption of individuals, trains operators in the use of field instruments, and maintains and services such instruments. The latent fingerprint unit processes and examines evidence for latent fingerprints. The polygraph unit administers and interprets the results of polygraph tests. The voiceprint analysis unit analyzes sound recordings to connect voiceprints to particular criminal suspects. The crime scene investigation unit dispatches specially trained personnel to the crime scene to collect and preserve physical evidence that will later be processed at the crime laboratory.

List the main functions of the forensic scientist

The main functions of the forensic scientist include analyzing physical evidence; providing expert testimony; and furnishing training in the proper recognition, collection, and preservation of physical evidence.

What important principle was established in the case of Frye v. United States?

Frye v. United States established the principle that questioned procedures, techniques, or principles must be "generally accepted" by a meaningful segment of the relevant scientific community before they are admissible as evidence at trial.

How did the court's ruling in the case of Daubert v. Merrell Dow Pharmaceuticals, Inc. affect the admissibility of scientific evidence in federal courts?

In Daubert v. Merrell Dow Pharmaceuticals, Inc., the Supreme Court asserted that "general acceptance" is not an absolute prerequisite to the admissibility of scientific evidence under the Federal Rules of Evidence. According to the Court, the Rules of Evidence assign to the trial judge the task of ensuring that an expert's testimony rests on a reliable foundation and is relevant to the task at hand.

How does the testimony of an expert witness differ from the testimony of a lay witness?

A lay witness must give testimony on events or observations that arise from personal knowledge. This testimony must be factual and, with few exceptions, cannot contain the personal opinions of the witness. By contrast, the expert witness evaluates evidence that the court lacks the expertise to do, and thus must express his or her personal opinion as to the significance of the findings. The views expressed are accepted only as representing the expert's opinion and may later be accepted or ignored in jury deliberations.

List two ways in which a forensic odontologist can assist in criminal investigations.

Forensic odontologists can use dental records such as X-rays, dental casts, and a photograph of a person's smile to compare a set of dental remains and a suspected victim. A forensic odontologist can also compare bite marks left on a victim to the tooth structure of suspects.

List six types of physical evidence derived from human or other animal sources that are commonly found at crime scenes.

Blood, semen, saliva, hair, fingerprints, organs, and physiological fluids are some types of physical evidence derived from human or other animal sources that are found at crime scenes.

List and define the two methods used by forensic scientists when examining physical evidence.

The two methods used by forensic scientists when examining physical evidence are identification and comparison. Identification is the process of determining a substance's physical or chemical identity. Comparison is the process of ascertaining whether two or more objects have a common origin.

To permit positive identification, testing procedures used by a forensic scientist must meet what two conditions?

To permit a positive identification, testing procedures must give characteristic results for specific standard materials. In addition, the number and type of tests required to positively identify a substance must be sufficient to exclude all other substances.

Describe the two steps in the process of comparison. What question does each step attempt to answer?

The first step in comparison is determining which properties from the suspect and the standard/reference specimen to compare. This step attempts to determine whether the two samples are the same. The second step is concluding the origins of the specimens. This step attempts to determine how likely it is that two samples came from the same source.

Define individual and class characteristics

Individual characteristics are properties of evidence that can be attributed to a common source with an extremely high degree of certainty. Class characteristics are properties of evidence that can be associated only with a group and never with a single source. Examples include paint and fibers

Define the product rule and explain how it can be used to determine whether two blood samples come from the same source.

The product rule states that one can obtain an overall frequency of occurrence for a genetic profile by multiplying together the frequencies of independently occurring genetic markers. If several different factors from two blood samples are found to be identical, a forensic scientist can apply the product rule to calculate how frequently blood containing that combination of factors occurs in the population. The more blood factors that match, the greater the probability that the two blood samples originated from a common source.

What is the greatest weakness of class evidence? List two factors that contribute to this weakness.

The greatest weakness of class evidence is that examiners cannot assign exact or even approximate probability values to the comparison of most class evidence. Few statistical data exist from which to derive comparative information for most class evidence, and society is increasingly dependent on mass-produced products that are extremely difficult to distinguish from one another.

What is the value of class evidence? Why is this important in making a case to a jury?

The value of class evidence lies in its ability to corroborate events with data that are, as nearly as possible, free of human error and bias. This is important because most other types of evidence (such as eyewitness testimony and confessions) are subjective in nature and susceptible to dispute, human error, or bias.

Why are some jurists wary of allowing unconditional use of scientific evidence in court?

Some jurists are wary about scientific evidence because juries often accord scientific evidence greater weight than other evidence, tend to consider it more trustworthy, and often view it with less skepticism. Without proper safeguards, the use of scientific evidence may unfairly prejudice a case against the accused.

How can the extreme sensitivity of modern analytical techniques hinder the process of comparing items of physical evidence?

When measured or examined with extreme precision, no two items—even those originating from the same source—are exactly alike. Thus, using an analytic technique that is too sensitive makes it impossible to meaningfully compare different items of evidence.

What are IAFIS and CODIS? Describe the purpose of each

IAFIS is the Integrated Automated Fingerprint Identification System, a national fingerprint and criminal history database maintained by the FBI. IAFIS allows criminal investigators to compare fingerprints at a crime scene to an index of 750 million known prints. CODIS is the FBI's Combined DNA Index System. It enables federal, state, and local crime laboratories to electronically exchange and compare DNA profiles, linking crimes to each other and to convicted offenders.