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Forensic Textbook chapter 3
Information pertaining to in class set textbook Forensics per chapter ---
Terms in this set (69)
What should the crime scene notes include?
The notes should include contact information, personnel information and movements, task assignments, observations of the victim and scene, and information about the evidence before and after it is processed
Recording notes on what is advantageous?
Recording notes on digital voice recorders is advantageous, but investigators must be careful to speak clearly and avoid including side conversations
The use of electronic means to capture light and save an image on a microchip
The rate at which the silver halide grains of a given film react to light
One million pixels; used to describe a digital camera in terms of sensor resolution (i.e. four megapixels equals four million pixels)
Single lens reflex (SLR or DSLR) camera
A type of camera that uses the same lens for viewing and for taking the picture. The image seen in the viewfinder or on the LCD monitor is how the photo will turn out.
The normal lens has a 50 to 55 mm focal length. It can be used for most photographs that need to be taken at a crime scene because it can capture as much area as half a wall. It can also take satisfactory photographs of pieces of evidence at standard distances
The telephoto lens is like a telescope attachment for the camera, capturing a close-up image of a distant object or subject. This lens has a focal length of 100 mm or greater. This means that a 200 mm telephoto lens, for example, produces an image that is four times the magnification of the normal 50 mm lens
A photographer who needs to capture a wider area uses a wide-angle lens with a focal length of less than 50 MM. The typical focal length of the wide-angle lens is 35 mm, and it can show much more area in one photograph than can a normal lens. For example, this lens is useful in photographing wide objects such as the facade of a building; it will capture more detail to the left and right of the center of the structure than will a normal lens
When very close photographs and good detail are required, the photographer might use a macro lens. The macro lens has a focal length of less than 50 mm and a 1:1 or 1:2 magnification ratio. It is especially useful for close-ups of fiber or tool mark evidence
A multipurpose lens, commonly called a zoom lens, can also be used for crime-scene photography. These lenses have a range of focal lengths, usually from 28 to 80 mm. This type of lens allows the photographer to take normal, wide-angle, and telephoto photographs without changing lenses
Most DSLR cameras have a fixed what?
Most DSLR cameras have a fixed normal or multipurpose lens, typically in the range of 14 to 55 mm, and accepts a variety of lenses
The size of the diaphragm opening through which light enters the camera
A setting on a camera that controls the aperture diameter to determine the amount of light transmitted through the lens to the film or microchip
The length of time that the film or microchip is exposed to the light
depth of field
The amount of area in the foreground and background of an in-focus photographic subject that is also relatively in focus
The measure of the "degree of whiteness" of a light source compared to a hypothetical source of perfect white light
What does illumination refer to?
Illumination refers to the light falling on an object in a photograph
What is film made of?
Film is made of a sheet of light-reactive silver halide grain. The light-capturing ability of the grains is called film speed, and high-speed films have bigger grains in order to capture light faster. This means that higher-speed films create grainier photographs
Why are filters used with SLR or DSLR cameras?
Filters are used with SLR and DSLR cameras to block certain wavelengths of light (barrier filters) or allow in only certain wavelengths of light (by-pass filters)
Tripods should be used because?
They greatly improve photograph quality by preventing blurriness caused by the movement of the photogrpaher;s hand. They also help ensure 90-degree close-up photographs of evidence
The form on which the investigator records the details of each photograph taken at a crime scene
What is the first basic guideline for crime-scene photography?
Photograph the crime in an unaltered condition:
What is the second basic guideline for crime-scene photography?
Fill the frame:
What is the third basic guideline for crime-scene photography?
Avoid shadows in the photograph
What is the fourth basic guideline for crime-scene photography?
Maximize depth of field
What is the fifth basic guideline for crime-scene photography?
Photograph the scene in a logical sequence
What is the six basic guideline for crime-scene photography?
Keep a log
What is an Overview photograph?
The first pictures the photographer taken are overview photographs of the entire scene and surrounding area
What do you include in an overview photograph?
The points of exit and entry.
What is a Medium-range photograph?
Medium-range photographs show the layout of smaller significant areas of the crime scene.
What should Medium-range photographs be taken with to show spatial relationships?
What is a key medium-range photograph standard?
A standard to all crime scenes is one that includes the "center" of the scene
What is a Close-up photograph?
The last pictures taken. Close-up pictures show the greatest detail of individual objects or evidence
What degree should close-up photographs be taken?
The pictures must be taken at a 90-degree angle to the object.
What can be included in close-up photographs?
Evidence markers and scales
4 photographs are the minimum to be taken at a crime scene. What type are these 4 photographs?
1. An overview photograph
2. A medium-range photograph
3. A close-up photograph
4. A close-up photograph with a scale
What do the crime scene photographs create?
A visual record of the position and appearance of an item of evidence at a crime scene
What are two methods for photographing at night?
Use of reflectors to focus flash illumination
If you photograph at night, what do you need in daylight?
All crime scene photographs taken at night should be repeated during daylight hours.
What should also be included in crime scene photographs at outdoor scenes?
Photographs of the street signs closest to the scene.
If a vehicle is included in the scene or is the scene what should you make special note of in crime scene photographs?
License plates and vin numbers
What do you need to pay attention to in photographs of accidents?
The photographs should not only note the site of the accident, but also of the approach . Photographers take photographs at various points of impact for reconstruction purposes
What is especially important to take a photograph of at an Arson investigation?
The crowd outside an arson scene
What is important to take photographs of in a sexual assault case?
The victim's clothes
What must you use when taking photographs of impressions?
A tripod: to ensure the film is arranged at 90 degrees
How do you take photographs of bloodstains detected with luminol?
Bloodstains detected with luminol must be photographed in complete darkness. The camera shutter is locked open for approximately three minutes at an f-stop of 22, and a flash at 1/16 power is fired at the beginning of the three minutes
Close-up photographs of latent fingerprints must show what?
Latent (hidden) fingerprint photographs must show ridge details of fingerprints of possible identification of their source.
What three things do you need to photograph at a shooting scene?
1. A 360 degree view of the site
2. the bullet: including any and all fragments
3. The damage done by the fired bullet including points of impact and any marks associated with ricochet
A compression method for digital files that decreases the file size without discarding digital data
How are digital images preserved?
By either lossy or lossless compression
How is video documentation helpful?
Video documentation is helpful for showing possible paths and for combining note narrations with photography
The rudimentary first sketch created at the crime scene with care for accuracy in depicting dimensions and locations but no concern for aesthetic appearance
What tools are required to create a sketch?
Graph paper or drawing paper
Two measuring tapes
Clipboard or drawing surface
Compass or GPS device
What are optional tools you can use to create a sketch?
protractors (half and full circle)
rolling measuring devices
Sketches must include what features?
body of sketch
What should the title block contain?
The title block contains the case number, the agency number (if applicable), the name and title of the artist, the location of the scene, and the date and time at which the sketch was created. It may also state the victim's name, names of any suspects, or type of crime
Where should the title block be located?
The title block should appear in the lower right corner of the sketch paper
What should the legend contain?
The legend should contain the key to the identity and dimensions of objects or evidence and may be represented by symbols, letters, or numbers
What should the compass show?
The compass should show an arrow to denote north in relation to the scene
What should the body of the sketch contain?
The body of the sketch contains the drawing itself and all dimensions and objects located within it
What is the rectangle method of measurement?
Measure two distances to an object that make a right angle with each other and to two fixed, flat surfaces. These surfaces are usually walls
What is the triangulation method of measurement?
Measures the distance of the object from two fixed points of known distance from each other. This forms a triangle.
In an indoor scene these points are usually the corners of a room
What is the baseline method of measurement?
First: two fixed objects on opposite sides of the scene are located. A line is then make between them and measured.
Each object or piece of evidence has a line drawn from it to the baseline to make a 90-degree angle with the baseline. This distance of the line from the object to the baseline is then measured, along with its point of intersection with the baseline
What is the baseline method of measurement especially useful for?
What is the polar coordinates method of measurement?
This method uses only one reference point. The sketch shows the distance and angle at which an object is located in the scene relative to the reference point
What can distances not be?
They can not be estimates of results of a guess
The perfected final sketch that is constructed with care and concern for aesthetic appearance and drawn to scale
Computer-aided drafting (CAD)
The process of creating a scaled drawing using specially designed computer software
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