Forensics Final Exam
What evidence does an investigator study to make a distance determination? How can test-firing a suspect weapon help the investigator make a distance determination?
The distribution of gunpowder particles and other discharge residues around the bullet hole permits an assessment of the distance from which a handgun or rifle was fired. To determine the precise distance from which a gun has been fired requires a comparison of the powder-residue pattern on the victim's clothing or skin against patterns made from test-firing the suspect weapon. By comparing residue patterns from test firings to those found at the crime scene, the examiner may find enough similarity in shape and density on which to base an opinion as to the distance from which the shot was fired.
Name two types of marks that impart individuality to a tool and explain how the marks are made.
The edges of any tool display a series of microscopic irregularities having the appearance of ridges and valleys. These marks are created during the machining processes used to cut and finish the tool. Another type of mark is caused by nicks and breaks in the tool that occur during normal use.
Why does a firearms examiner test-fire bullets from a suspect barrel?
The examiner must test-fire bullets through the suspect barrel because there is no other practical way to directly compare the markings on the fired bullet and those found within a barrel.
Describe how a firearms examiner compares two bullets. What characteristic does an examiner most often use to identify bullets and why?
The examiner places both bullets under a comparison microscope, pointing in the same direction, and then rotates one bullet until a well-defined land or groove comes into view. When the examiner locates striation markings on this bullet, the other bullet is rotated until a matching region is found. When a matching area is located, the two bullets are simultaneously rotated to locate additional matching areas around the periphery of the bullets. The examiner uses the striation markings to identify bullets because no two rifled barrels have identical striation markings.
What is the final step in fingerprint identification? Why is this step necessary if a computerized database of fingerprints is available to the forensic scientist?
The final step in fingerprint identification is always visual comparison of the prints in question by a trained examiner. A computer database can only produce a list of prints that are similar to the print in question; it cannot make a positive identification.
Besides the barrel, what parts of a firearm may leave distinctive markings on a shell cartridge?
The firing pin, the breech-face, the extractor, the ejector, the magazine, the clip, and the fire chamber walls may all leave distinctive markings on a shell casing.
What aspect of a fingerprint determines its individuality?
The identity, number, and relative location of ridge characteristics impart individuality to a fingerprint.
What characteristics of a suspect firearm should an investigator record before unloading it? Why should the investigator number the chambers and cartridges when unloading a suspect weapon?
The investigator should record the weapon's hammer and safety position as well as the location of all fired and unfired ammunition in the weapon. The cylinders and cartridges should be numbered because this information may be useful to determine the sequence of events, particularly in cases in which several shots were fired.
What is the most commonly used chemical method to visualize latent fingerprints on porous materials? If this method is unsuccessful, what other technique typically is used?
The ninhydrin method is most commonly used to visualize latent fingerprints on porous materials. If the ninhydrin method fails, the Physical Developer technique is typically used.
The writing characteristics of a person may be altered by whether;
The paper is ruled or unruled. Pencil, ballpoint, or fountain pen is used. The posture or stance of the author varies between writings.
What phenomenon underlies many of the new chemical techniques used to visualize latent fingerprints? Why is this phenomenon so valuable in fingerprint visualization?
The phenomenon of fluorescence serves as the underlying principle of many of the new chemical techniques used to visualize latent fingerprints. Substances that emit light or fluoresce are more readily seen either with the naked eye or through photography as compared to non-light-emitting materials. Thus, techniques based on fluorescence permit better visualization of all prints and allow the visualization of faint prints that other methods may fail to visualize.
List two reasons why striations on bullets fired from the same gun may vary slightly.
The presence of grit and rust can alter the markings on bullets fired through the same barrel. Striation markings on a barrel are not permanent structures; they are subject to continuing change and alteration through wear as succeeding bullets traverse the length of the barrel.
What aspect of a fingerprint forms the basis for primary classification under the FBI system? What is the main drawback of the FBI system?
The presence or absence of the whorl pattern is the basis for determining the primary classification in the FBI system. The main drawback of the FBI system is that it is useful only when a full set of fingerprints is available.
What is the investigator's primary concern when collecting and handling bullets and cartridge cases? Why must the investigator exercise extreme caution when removing a bullet lodged in a wall or other object?
The protection of class and individual markings on bullets and cartridge cases must be the primary concern of the field investigator who is handling such evidence. If the bullet's surface is accidentally scratched when removing it from a wall or other object, valuable striation markings could be obliterated that can help link the bullet to a suspect weapon.
A threatening letter is received by a company CEO via fax. What characteristics can be examined to gain information about the sending machine, the sending individual, and fraudulent source information?
The sending fax machine will print a header known as the transmitting terminal identifier (TTI) at the top of each fax page. The header and the document's text should have different type styles. TTIs can be fraudulently prepared and placed in the appropriate position on a fax copy. However, a microscopic examination of the TTI's print quickly reveals significant characteristics that distinguish it from a genuine TTI. Information about the sending individual can be gained from analysis of the letter's spelling, punctuation, phraseology, and grammar.
What kinds of impression evidence might a forensic odontologist be asked to analyze? How might this help identify a suspect?
A forensic odontologist might be asked to analyze bite marks on a person or object found at a crime scene. If a sufficient number of points of similarity exist between the test and suspect marks, the forensic odontologist may conclude that the marks were made by one particular individual.
When should a fingerprint be "lifted" from a crime scene? Describe how to lift and preserve a fingerprint using adhesive tape.
A print should be "lifted" from a crime scene when it is on a large, immovable object. One method of lifting is to dust the print with fingerprint powder, then cover the print with adhesive tape. When the tape is pulled up, the powder is transferred to the tape. Then the tape is placed on a card that provides a good background contrast with the powder.
Briefly describe how the Automated Fingerprint Identification System (AFIS) creates a fingerprint image. What characteristics of the fingerprint does the AFIS record for comparison?
AFIS scans fingerprints and converts them into digital images that contain data on the relative location and orientation of ridge characteristics. The system records the points where ridges terminate, the points where they branch into two ridges, and the relative position and orientation of each ridge characteristic.
When dictating to a person in order to obtain samples of handwriting, one should NOT:
Allow the suspect to view the questioned document before dictating it
Why would an investigator not pick up a weapon by its barrel with a pencil or stick in order to protect latent fingerprints? How should suspect firearms be handled in such a situation?
An investigator would not pick up a weapon by its barrel with a pencil or stick in order to protect fingerprints because this may disturb powder deposits, rust, or dirt lodged in the barrel, and consequently may alter the striation markings on test-fired bullets. If the recovery of latent fingerprints is a primary concern, it is best to hold the weapon by the edge of the trigger guard or by the checkered portion of the grip.
Why does analysis of primer residue from a suspect's hands produce a low rate of positive results? Why is such analysis typically ineffective in locating primer residue from a .22-caliber gun?
Analysis of primer residue from a suspect's hands produces a low rate of positive results because primer residues remain on the hands only for a short time and are easily removed by rubbing or washing. This technique cannot be used to detect firings with most .22-caliber rim-fire ammunition because the primer for this ammunition often does not contain characteristic elements associated with primer residues.
What is the first thing the investigator does before handling or moving any impression at a crime scene? Why is this considered merely a backup or precautionary procedure?
Before any impression is moved or otherwise handled, it must be photographed to show all the observable details of the impression. Photography is considered merely a backup procedure in case the impression is damaged before reaching the crime laboratory. It is preferable for the examiner to receive the actual impression for comparison to the suspect object that made the impression.
Any document that has become darkened and brittle through exposure to fire or excessive heat
Charred Document
When a suspect computer printer is not available, the examiner may need to analyze the document's ________ to identify the make and model of the machine.
Class characteristics
Questioned documents include;
Contracts and passports. Petitions and lottery tickets Letters and checks
What evidence do investigators look for when trying to determine whether a suspect has fired a handgun? Where is such evidence typically found and why?
Current efforts to identify a shooter center on the detection of primer residues deposited on the hand of a shooter at the time of firing. Residues are most likely to be deposited on the thumb web and the back of the firing hand of a shooter, because these areas are in closest proximity to gases escaping along the side or back of the gun during discharge.
Infrared luminescence is used to:
Detect if two different inks were used in the writing of a document. Reveal writing that has been erased.
What is digital imaging and how is it used in fingerprint analysis? What is the greatest limitation of digital imaging?
Digital imaging is a process through which a picture is converted into a series of square electronic dots known as pixels. It is used to compare fingerprints and to enhance poor fingerprint images. The main limitation of digital imaging is that it is only as useful as the images it has to work with. If the images are poor or incomplete, enhancement procedures will not work.
The process by which the image is stored in memory
Digitizing
What is the process by which the image is stored in memory by scanning and converting by computer into an array of digital intensity values called picture elements?
Digitizing
How is shot pattern used to make a distance determination for shotgun blasts? What factors other than distance to target can affect the distance determination?
Distance determination for a shotgun blast is made by measuring the spread of the discharged shot—the wider the spread, the farther the shooter was from the target. Other factors include the barrel length, the size and quantity of the pellets fired, the quantity of powder charge used to propel the pellets, and the choke of the gun (the degree of constriction placed at the muzzle end of the barrel).
What is distance determination? Describe two situations in which distance determination can establish the facts of a shooting incident.
Distance determination is the process of determining the distance between the firearm and a target, usually based on the distribution of powder patterns or the spread of a shot pattern. If a suspect pleads self-defense as the motive for a shooting, determining how far apart the suspect and victim were at the time of shooting can establish the facts of the incident. It can also determine whether a shooting was suicide, which usually involves a very close-range gunshot wound. The absence of characteristics consistent with a close-range shot is a strong indication that the wound was not self-inflicted and signals the possibility of foul play.
Which is an example of an impact printer?
Dot matrix
The removal of writing, typewriting, or printing from a document, normally accomplished by either chemical means or an abrasive instrument
Erasure
An authentic sample used for comparison purposes, such as handwriting
Exemplar
________ are authentic samples of an individual's writing used for comparison to suspect handwriting samples.
Exemplars
Indented writings are not readable under any typical examinations.
False
Margins, spacing, crowding, insertions, alignment, spelling, punctuation, phraseology, and grammar cannot impart individual variations.
False
Variations in vertical and horizontal alignment cannot be used to identify a typewriter.
False
When comparing sample writing to a suspect document, the age difference between the documents should be no more than six to twelve months.
False
Defects that are reproduced by a photocopier onto a copied document may originate from defects in all of the following photocopier parts EXCEPT:
Feed tray
With regard to the constitutionality of obtaining handwriting exemplars, the courts have ruled all of the following EXCEPT:
Fifth Amendment privileges apply
Who published the first book on the science of fingerprinting? What were the book's most important contributions to understanding fingerprints?
Francis Galton published the first book on the subject of fingerprinting. The book's most important contributions were to demonstrate that no two prints are identical and that an individual's prints remain unchanged from year to year.
In the case of ________, the Supreme Court held handwriting to be nontestimonial evidence not protected by Fifth Amendment privileges
Gilbert v. California
The ease with which one can find individual variations in a typewritten document is ________ the ease of finding such defects in documents produced by business and personal computers.
Greater than
List three characteristics of a bullet hole that indicate that the shot was fired at extremely close range.
If the weapon is fired less than 1 inch from the target, a heavy concentration of smokelike vaporous lead usually surrounds the bullet entrance hole. Often, loose fibers surrounding a contact hole show scorch marks from the flame discharge of the weapon, and some synthetic fibers show signs of being melted as a result of the heat from the discharge. Furthermore, the blowback of muzzle gases may produce a stellate (star-shape) tear pattern around the hole.
________ printers include thermal and dot-matrix printers.
Impact
Applying an electrostatic charge to the surface of a polymer film that has been placed in contact with a questioned document can be used to read ________ writing.
Indented
________ writings are partially visible impressions appearing on a sheet of paper underneath the one on which the visible writing was done
Indented
impressions left on paper positioned under a piece of paper that has been written on
Indented writings
A warranted search of a victim's apartment yields three pages of exemplar handwriting samples written on ruled notebook paper with blue ballpoint pen. The investigators would like to compare the handwriting on these exemplars to a potential suicide note found with the dead victim written on unruled paper in pencil. Based on this information, which characteristics of the handwriting can be used to compare the exemplar documents and questioned document? Which characteristics cannot be used, and why?
Individual variations may be expected in angularity, slope, speed, letter and word spacings, connections, writing skill, finger dexterity, crowding, insertions, spelling, punctuation, phraseology, and grammar. The investigator cannot use the characteristics of relative dimensions of letters, alignment, margins, and spacing between lines because these characteristics are affected by the ruled or unruled nature of the paper. Apparent pressure applied cannot be used because this characteristic is affected by the writing implement and paper used.
Some inks, when exposed to blue-green light, absorb ________ radiation and emit light
Infrared
________ luminescence can be used to detect alterations to a document made with ink differing from the original and can also reveal writing that has been erased.
Infrared
A property exhibited by some dyes that emit infrared light when exposed to blue-green light
Infrared luminescence
The property exhibited by some dyes that emit infrared light when exposed to blue-green light is known as:
Infrared luminescence
A small piece of paper from a hotel notepad is found in the pocket of a potential "hit man" as he attempted to kill his "mark." The paper shows writing in various pen colors, some of which is obliterated and some of which was erased. The top corner of the paper also appears to possess intended writing. Discuss the methods investigators should employ to visualize the writing if possible.
Infrared luminescence can be used to detect alterations to a document made with ink differing from the original. Infrared luminescence can also reveal writing that has been erased. Indented writings are often readable when the paper is studied under oblique or side lighting. A second method involves applying an electrostatic charge to the surface of a polymer film that has been placed in contact with a questioned document. Indented impressions on the document are revealed by applying a toner powder to the charged film.
Document examiners frequently uncover the original writing of words that have been crossed out with the aid of:
Infrared radiation
The ease with which a child's handwriting can be individualized is ________ the ease with which one can individualize an adult's handwriting
Less than
The possibility of recognizing known writing habits in samples produced when a writer is under the influence of drugs or alcohol is ________ the possibility of recognizing known writing habits produced when the writer of a sample is not under the influence of drugs or alcohol.
Less than
Normal deviations found between repeated specimens of an individual's handwriting
Natural variations
What are natural variations? How can they be useful for detecting forgeries?
Natural variations are normal deviations found between repeated specimens of an individual's handwriting. They are useful in detecting forgeries because no two specimens of writing prepared by one person are ever identical in every detail. Thus, a document forged by tracing an authentic sample of writing or a signature can often be detected even if the original and the tracing coincide exactly, because no one ever writes the same words or signs two signatures exactly alike.
________ printers include inkjet and laser printers.
Nonimpact
Blotting out or smearing over writing or printing to make the original unreadable
Obliteration
Which of the following statements is FALSE?
Once adulthood is reached, an individual's handwriting generally will not change with age
Transitory defect marks originating from random debris on the glass platen are examples of points of comparison produced by a ________.
Photocopier
If an investigator is to prepare standards from a suspect typewriter, which procedure is recommended?
Prepare at least one copy of the text in full word-for-word order
Which are important characteristics of a printer, photocopier, or fax machine?
Printing technology Type of paper Type of toner or ink used
A(n) ________ document is any object that contains handwritten or typewritten markings whose source or authenticity is in doubt.
Questioned
Any document about which some issue has been raised or that is the subject of an investigation
Questioned document
A databank of ink dye patterns has been established by the U.S. Treasury Department using:
TLC
A header that fax machines print
TTI
Fax machines print a header known as the ________ at the top of each fax page, which may become a very important point of comparison.
TTI
What is the Greiss test and what two pieces of information can it provide to an investigator?
The Greiss test is a chemical test used to develop patterns of gunpowder residues around bullet holes. The test results can reveal whether powder residues from a gunshot are present and can also help determine the distance from the shooter to the target.
What is the dermal papillae and why is it important in fingerprinting?
The dermal papillae is a boundary of cells separating the outer portion of the skin (epidermis) and the inner skin (dermis). The shape of the dermal papillae determines the form and pattern of the ridges on the surface of the skin. Because the dermal papillae does not change shape throughout life, the ridge patterns of fingerprints also do not change.
Describe each of the three classes of fingerprints. Which class is the most common in the population? Which is least common?
The three classes of fingerprints are loops, whorls, and arches. Loops are characterized by ridge lines that enter from one side of the pattern and curve around to exit from the same side of the pattern. Whorls include ridge patterns that are generally rounded or circular in shape and have two deltas. Arches are characterized by ridge lines that enter the print from one side and flow out the other side. Loops are most common; arches are least common.
Two analytical techniques used to analyze writing inks are microspectrophotometry and ________ chromatography.
Thin-layer
Inks on handwritten documents may be compared for their chemical composition by the technique of:
Thin-layer chromatography
List three class characteristics of a gun barrel.
Three class characteristics of a gun barrel are its caliber, the number of lands and grooves, and the direction and twist of the lands and grooves.
Why is it almost impossible to obscure one's fingerprints by surgery or mutilation?
To obscure one's fingerprint, an injury or surgery must reach deeply enough into the skin to damage the dermal papillae. Even so, it would be totally impossible to obliterate all of the ridge characteristics on the hand. Any attempt to do so would create deep scars that would provide new characteristics for identifying one's prints.
Describe how a criminalist restores an obliterated serial number on a weapon.
To restore an obliterated serial number, the criminalist applies a suitable etching agent to the area that has been defaced. The metal in this area dissolves at a faster rate than the unaltered metal surrounding it, thus permitting the etched pattern to appear in the form of the original numbers.
Angularity, slope, and speed are examples of individual variations
True
Examination of toner typically involves microscopic analysis followed by identification of the inorganic and organic components.
True
Infrared luminescence can reveal writing that has been erased.
True
No two specimens of writing prepared by one person are ever identical in every detail.
True
The most common features associated with a paper examination are general appearance, color, weight, and watermarks.
True
The two general categories of printers are impact and nonimpact printers
True
Two analytical techniques used to analyze writing inks are microspectrophotometry and thin-layer chromatography.
True
List two types of specialized fingerprint powders and name one advantage each has over traditional fingerprint powder.
Two specialized fingerprint powders are magnetic-sensitive powder and fluorescent powder. Using magnetic-sensitive powder offers less chance that the print will be destroyed or damaged because the powder is spread using a magnetic brush that has no bristles to come in contact with the surface containing the print. Fluorescent powders reveal a vivid image of a print under ultraviolet light. When the developing print is photographed under UV light, the color of the surface will not obscure the print.
When comparing sample writing to a suspect document, the age difference between the documents should be no more than:
Two to three years
In dealing with fax machines, photocopiers, and computer printers, which class characteristics might be examined?
Type of paper Chemical composition of toner Type of toner-to-paper fusing method
List and describe the three types of fingerprints that may be found at a crime scene.
Visible prints are made when a finger deposits a visible material such as ink, dirt, or blood onto a surface. Plastic prints are ridge impressions left on a soft material such as putty, wax, soap, or dust. Latent or invisible prints are impressions caused by the transfer of body perspiration or oils present on finger ridges to the surface of an object.
What major advance in fingerprint technology was pioneered by Juan Vucetich and Sir Richard Henry? What was the importance of this advance?
Vucetich and Henry pioneered the creation of classification systems capable of filing many thousands of prints in a logical and searchable sequence. This allowed law enforcement officials to quickly compare prints found at a crime scene to those of known criminals as an aid to identifying potential suspects.
Describe two situations in which a document examiner may be prevented from coming to a positive conclusion about a questioned document.
When an insufficient number of known writings are made available for comparison When the examiner receives questioned writings containing only a few words, all deliberately written so as to disguise the writer's natural style
What techniques does an investigator use to analyze tool marks that cannot be removed from a crime scene? What is the disadvantage of this technique?
When removal of the tool mark is impractical, the area is photographed and marked to scale, and a silicone cast of the mark is made. The disadvantage of this technique is that even under the best conditions, the clarity of many of the tool mark's minute details will be lost or obscured in a photograph or cast.
Name five important characteristics of a printer, photocopier, or fax machine that a document examiner must identify when analyzing a document in a situation where the suspect machine is not available.
When the suspect machine is not available, it is important to identify the printing technology, the type of paper, the type of toner or ink used, the chemical composition of the toner, and the type of toner-to-paper fusing method used in producing the document.
A TTI cannot be used to distinguish between a real and a fraudulently prepared fax document
false
Nonimpact printers include thermal and dot-matrix printers
false
Investigators can use a TTI to determine the model of ________ machine that produced the document.
fax
The TTI is a characteristic used to distinguish:
fax machines
Overwriting or crossing out writing is known as:
obliteration
A TTI is a characteristic of a fax document
true
An adequate number of exemplars is critical for determining the outcome of a comparison.
true
