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Forensic Archiving I

Forensic Archiving I. Forensic Archiving Refers to preserving scene’s record . A departure from usual terminology Encompasses more than simply photography, sketching, or imaging . Has modern relationship with a digital world .

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Forensic Archiving I

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  1. Forensic Archiving I

  2. Forensic Archiving • Refers to preserving scene’s record. A departure from usual terminology • Encompasses more than simply photography, sketching, or imaging. • Has modern relationship with a digital world. • Photography, is a sub-category under the umbrella of the broader and more relevant term, forensic archiving. • Term: Documentation: • A Current standard no longer reflects current practice. • Times change as does a profession’s lexicon. [1] American Heritage College Dictionary Third Edition, Houghton Mifflin Company, 1993. [2]http://www.pcmag.com/encyclopedia_term/0,2542,t=active+archiving&i=37447,00.asp#. Accessed 3/20/2009.

  3. Definitions • The American Heritage College Dictionary: • “archive” a noun, “A place or collection containing records, documents, or other materials of historical interest.” • Modern computer usage uses “archive”: • A verb … backing up digital files, and PC Magazine and defines “Active Archiving” as, “Moving data to a secondary storage medium that can be readily accessed if required.” • Appropriate considered in light of current crime scene practice as well as what happens afterward • DOCUMENTATION • The act or an instance of furnishing or authenticating with documents • The provision of documents in substantiation; also: • Documentary: • the use of historical documents • conformity to historical or objective facts • the provision of footnotes, appendices, or addenda referring to or containing documentary evidence [1] American Heritage College Dictionary Third Edition, Houghton Mifflin Company, 1993. [2]http://www.pcmag.com/encyclopedia_term/0,2542,t=active+archiving&i=37447,00.asp#. Accessed 3/20/2009.

  4. Archiving Essentials • Critical responsibility of crime scene investigative unit, • Preserve the scene as found, so that anyone can “see” what original investigators saw. • The essence of the scene is critical … impossible to predict when another pair of eyes will need to review the “original.” • No single archiving method is sufficient, • Taking notes, • Writing reports • Increasingly complex technology. • Video alone is insufficient and inadequate as are the newer 3D archiving systems, though they are certainly capable of providing more accurate measurements. • Each method has attributes and deficiencies • A complete and competent archive of the scene requires a battery of techniques.

  5. Crime scene record is put into an archive where the historical record of the crime scene exists. • The crime scene archive is, in fact, a place • which can be a case file, • a file cabinet, • digital photos on a computer hard drive or a CD backup or both. • Contemporary investigations - employ a form of digital media: • Photos taken using a digital SLR camera, • Digicamvideo recorder, • CAD computer system, software to enhance images, or • 3D digital imaging systems. • Hand drawn sketch & investigator notes … captured digitally, as well as the hand written notes of an investigator. • The mechanism used to archive the scene should include multiple techniques.

  6. Forensic PhotographyAn Essential SkillTelling The Scene’s Story

  7. The Purpose of Forensic Photography • Why Photograph the Scene? • “To archive the scene.” An activity with far reaching implications. The most obvious are straight forward. • Record and preserve the as-found condition of the scene • Show the relative position of evidence at the scene • Establish the relative dimensions of evidence • Complement other archiving techniques

  8. Other Reasons • Hypothetical Case • Defendant is convicted of a murder and sentenced to life imprisonment or even the death penalty. If, on appeal, the defense finds potentially exculpatory evidence and a judge rules that the convicted defendant should be granted a new trial, the investigation begins again. • New investigators – defense and prosecution – • Find new evidence to support original conviction or an acquittal. • First: View the photographs of the original scene.

  9. Active vs. Passive Archiving • Active archiving: Process of combining the “rote,” the passive aspect of archiving, with an engaged brain. Thinking critically about relationship of evidence to the scene • Passive Archiving: Overview photographs of a room of a dead body, moving from different areas and snapping photographs without considering what is being captured. • EXAMPLE • Should capture body on the floor in a pool of blood … AND capture knife sticking out from under the deceased’s forearm? • Is the depth of field OK to include that AND the knife sticking out • from under the sofa six feet behind the deceased’s body?

  10. Active vs. Passive Archiving • Failing to capture the knife in either perspective might mean missing critical part of the eventual scene reconstruction. • In the case, the single-line cast off blood pattern on the wall behind where the body lies is likely from castoff from a knife. AND should be in the same perspective as the body and the knives. • Need to understand the relationship of all items of potentially probative evidence. • Requires: thinking carefully about each and every photograph. • Robots do not “think.” They just “do.”

  11. Photography: Is Integral Part of Scene Search • Part of visible investigation … search of scene. • An essential part of an active investigation. • Recreational and forensic photography part ways. • The artist is trying to be creative in order to capture the scene from an artistic sense. • Forensic investigations are not artistically creative, but creative in the sense that the photographs capture the best perspectives in order to capture the scene’s story. • Artist allows the landscape to guide the artistic process, • Forensic photographer allows the scene to guide the continuum of photographs in the same way: from relevant evidence to relevant evidence. • Paradoxically: forensic photographer must capture EVERYTHING.

  12. Single Lens Reflex Cameras - SLR

  13. Managing Your Camera

  14. Why SLR’s? • Lenses can be changed in order to meet specific photographic challenges • The investigator sees exactly what the lens “sees.” • Unless camera is modified for IR photography. • Digital SLRs have large image sensors that produce high-quality photos. • An SLR has a near-zero lag time.

  15. Essential Skills of Forensic Photography • Focus: If not in focus, the rest doesn’t matter • Digital Cameras: The LCD viewer allows for immediate inspection of focus. • CAVEAT: LCD …Small image …out-of-focus photographs appear in focus, but out of focus when viewed on on the computer screen. • Use the LCD as a guide of focus • Concept: Tack Sharp: Photographs in sharp focus • Blurry photographs are of little use and serve no investigative purpose. [1] Kelby, Scott – Chapter 1 – Pro Tips for Getting Really Sharp Photos. In The Digital Photography Book, Volume 1. Peachpit Press 2006, page 1.

  16. Focus • Use tripod with a ballhead or at least a monopod. • There are situations when hand-held is the only way to get the correct photograph. • Pressing shutter moves the camera. • Use cable release, • self timer function • infrared wireless remote . • Lock the camera’s mirror in the up position. • Camera moves the mirror up and locks it while taking the photograph which causes movement. • Move the mirror up manually Exposure Delay Mode (Nikon) or Mirror Lockup (Canon) . • Vibration Reduction (VR) (Nikon) or Image Stabilization (IS) (Canon) minimize vibration from pressing the shutter. • Rules of thumb: • 1. If you are hand-holding the camera, activate the VR system, and • 2. If the camera is on a tripod, inactivate the VR system.

  17. Focus • Shoot at the lens’ sharpest aperture - about two full stops smaller than wide open. • If the lens is f/2.8, the best apertures would be f/5.6 and f/8 (two full stops down from 2.8). • Each lens has a sweet spot that delivers its sharpest images. • High quality lenses make a difference. Use high quality “glass” for tack sharp photographs. • Avoid high ISO’s if possible. • On a tripod in dim light … do not increase the ISO. Keep the ISO at the lowest possible setting. • Resulting photographs will be sharper. If hand holding in dim light, may be impossible to get the photograph without using a higher ISO. .

  18. Focus • LCD on the camera back unreliable gauge of focus, • Use the zoom feature to examine the photograph detail for focus. • Out-of-camera image manipulation • Software manipulation of images for forensic purposes is not necessarily bad - must remain with modification. • Trend to avoid or not even allow software manipulation of photos. Burden is on photographer to capture forensically perfect photographs every time. • Hand-holding the camera increases the likelihood of obtaining out-of-focus photographs • Use the camera’s burst function. One of the resulting photographs will be in focus. • In hand-holding situations, bracing the camera against something, e.g., wall, a railing, etc., can steady it sufficiently to obtain sharp photographs.

  19. Photographic BasicsThe Essential Terms - & Considerations Important Considerations Exposure Aperture Shutter ISO Focal Length Depth of Field White Balance Light

  20. Correct exposure is a lot like collecting rain in a bucket. • While the rate of rainfall is uncontrollable, • three factors remain under your control: • the bucket's width, • the duration you leave it in the rain, • quantity of rain you want to collect. • You just need to ensure you don't collect too little ("underexposed"), but that you also don't collect too much ("overexposed"). • The key is that there are many different combinations of width, time and quantity that will achieve this. For example, for the same quantity of water, you can get away with less time in the rain if you pick a bucket that's really wide. Alternatively, for the same duration left in the rain, a really narrow bucket can be used as long as you plan on getting by with less water. • UNDERSTANDING EXPOSURE http://www.cambridgeincolour.com/tutorials/camera-exposure.htm

  21. Definitions: • Exposure: Amount of light entering the camera. It has been defined as, • “the duration and amount of • light needed to create an image.” • Stop: The basic unit of exposure … where one stop is the equivalent of doubling or halving the amount of light entering the camera. • Controlling exposure allows the photographer to obtain that perfect forensic perspective, the one

  22. Exposure • Exposure:Tells the best forensic story. Only then does the photograph have the correct forensic exposure. • Correct forensic exposure controls light entering the camera so that the scene can tell its “story.”

  23. ApertureThe First & Most Critical DecisionAbout Exposure Begins with Aperture

  24. Aperture • Size of the hole through which light enters the camera. • Covered by a mechanical shutter that closes more quickly or more slowly (shutter speed) • Limits the time the digital sensor is exposed to the light. • Camera settings used to adjust the size of the hole • Terminology is f-stops or f/numbers. • Confusing and counterintuitive because the larger the f/number, say f/11 or f/22, the smaller the hole and visa versa. • Wide • f/stop or aperture of f/2.8 is wide - hole is larger • Narrow • f/stop of f/22 is a narrow opening – hole is smaller. http://en.wikipedia.org/wiki/Aperture

  25. An exposure control ring found in many modern SLR. The various setting may be represented by a few symbols/letters, "P" is for "Programmed AE", the "Tv" is for shutter priority while the Av (aperture value) is referring to aperture priority - Canon's way of interpreting in their A and T series camera bodies. Newer autofocus SLR cameras set aperture via the lens aperture ring; instead - aperture is controlled by the thumb wheel for BOTH shutter Speed (B) and Aperture (A). A method first pioneered by Canon on their manual focus Camera, the Canon T90 back in 1986. The VISIBLE confirmation of the selected aperture used on camera like this type is via the LCD on the top panel OR through the viewfinder. http://www.mir.com.my/rb/photography/fototech/apershutter/aperture.htm

  26. Aperture - Basics Diaphragm Lens opening 2x Light Stop Down 1 Full Stop f/4 ½ Light f/5.6 f/8 f/11

  27. Telling the Scene’s Story • The Importance of Aperture • Aperture is one of the big three players in solving the correct forensic exposure puzzle, • Aperture should be FIRST setting of photographer based on the photographer’s assessment of the appropriater perspective needed • Aperture allows scene to tell its story. • Each photograph has a specific forensic perspective the photographer must capture. • What at the scene and what in this photograph should be in focus? • What needs to be captured for the scene to tell its story

  28. Aperture: Forensic Equivalent of Archiving Gold. • It is the first camera setting that controls the most important perspective of the crime scene: What is in focus. • By choosing the aperture setting first, not just determining what is in focus at the scene, but is making that decision after critically evaluating the scene. • Determining the correct perspective.

  29. Depth of FieldWhat is in FocusDetermined by the Aperture Setting

  30. Depth of Field (DOF) • The concept of what is in focus in a photograph refers to a concept known as “depth-of-field,” or DOF. • Photographer must consider the DOF because it tells the scene’s story. • Aperture & DOF are intimately associated. • Size of opening on camera • Controls what at the scene is in focus in a photograph.

  31. 80-400mm zoom lens @ 400mm f/32, 1/30sec

  32. 80-400mm zoom lens @ 400mm f/5.6, 1/1000sec

  33. f/4, 1/500sec f/5.6, 1/250 sec 35-70mm zoom lens @ 35mm Equivalent Exposures f/22, 1/15 sec

  34. f/4 – 800th sec – ISO 1250 f/5.6-500th sec - Iso1250 d

  35. f/11 – 125th sec – ISO 1250 f/20 – 40th sec – ISO 1250

  36. Depth of Field - Rule of Thumb Establishing (Overview) Shots • For Maximum Depth of Field • Focus about 1/3 of the Distance into the Scene • DOF: One third in front • Three quarters beyond

  37. Where to Focus at the Scene Blood Pool 15ft 28ft Knife 15ft Window 5ft Door Small focal length wide-angle lens …… 24mm Focus @ 10’ – just in front of the body • Strive for: Maximum Depth of Field • Shorten focal length • Smaller aperture opening (larger f/number) • Greater distance to point of focus (evidence)

  38. Shutter SpeedHow Long is the Exposure

  39. Shutter Speed • Shutter Speed: The speed the shutter closes. • The shutter is the door to the outside world that remains open for fixed periods of time measured in seconds. • Closes the aperture to outside • Controls amount of light entering camera • Regardless of size of the opening, if the digital sensor is exposed too long, the resulting photograph will over exposed and will not meet forensic or artistic standards. • Role of the shutter is to control light getting to digital sensor, by opening and closing the cover over the aperture.

  40. Typical Shutter Speeds Typical shutter speeds • Older cameras: • shutter speeds set to halve or double light allowed in • 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, etc • Newer cameras • 1/3rd steps • 1/500, 1/400, 1/320, 1/250, 1/200, 1/160, 1/124, 1/100, 1/80, 1/60, etc http://photographylife.com/what-is-shutter-speed-in-photography

  41. Focal Length 12-24mm The distance (mm) from the center of the lens to where the image comes into critical view 18-55mm 55-200mm Object Photo’d Distance from Object Photographed

  42. Concept: Equivalent Exposures: Important for forensic photography • Different camera settings allow SAME amount of light to enter the camera but the resulting photographs are subtly different. • Known as equivalent exposures. • Equivalent Exposures • f/8 – f-stop and ¼ second shutter speed • f/11 – f-stop and ½ second shutter speed • f/16 – f-stop and 1 second shutter speed

  43. Aperture & Shutter Speed Equivalent Exposures The combination f/2.8 and shutter speed 1/125 sec gives a cell with number 10.  If you do two stops on the right and towards the top of the chart, you will get the number 10 again. http://irinaovery.com/wp-content/uploads/2012/03/2124175721_591714ec93.jpg

  44. Suggested Shutter Speeds for Photographing Variety of Subjects • When taking a photo of a moving subject, changing the shutter speed can change the look of an image. • A slow shutter speed captures movement. • Fast shutter speed freezes action.

  45. ISOThird Leg of the Exposure PuzzleDigital Processor SensitivityInternational Organization of Standards

  46. ISO • ISO Rating: Third leg of the exposure puzzle • Measure of the digital sensor’s sensitivity to light. • The higher the ISO number, the more sensitive the sensor is to light. • ISO settings affect exposure:Change in ISO from 100 to 200 effectively doubles the light available to the photograph … a full stop. • More light is not entering the camera • Digital sensor is more sensitive to light, which in essence changes the sensitivity of the camera a full stop.

  47. ISO 100 ISO 3200 http://www.digital-photography-school.com/iso-settings

  48. ISO Considerations • Most people keep digital cameras in ‘Auto Mode’ where the camera selects the appropriate ISO setting depending upon the conditions you’re shooting in (it will try to keep the ISO as low as possible) • Overriding the camera impacts the aperture and shutter speed needed for a well exposed shot. For example – • if you bumped your ISO up from 100 to 400, you can shoot at higher shutter speeds and/or smaller apertures. • Choosing the Correct ISO setting • Light – Is the subject well lit? • Grain – Do I want a grainy shot or one without noise? • Tripod – Am I using a tripod? • Moving Subject – Is my subject moving or stationary? • If plenty of light - AND need no grain in photo – AND using a tripod - AND subject is stationary. Use pretty low ISO rating. ject • If it’s dark – AND want grain - AND don’t have tripod – AND subject is moving. Consider increasing the ISO - Can shoot with a faster shutter speed and still expose the shot well. • Trade off of increase in ISO is noisier (grainer) shots.

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