Forensic photography
Encyclopedia
Forensic photography, sometimes referred to as forensic imaging or crime scene photography, is the art of producing an accurate reproduction of a crime scene
or an accident
scene using photography
for the benefit of a court or to aid in an investigation. It is part of the process of evidence
collecting. It provides investigators with photos of victims, places and items involved in the crime. Pictures of accidents show broken machinery, or a car crash, and so on. Photography of this kind involves choosing correct lighting
, accurate angling of lenses
, and a collection of different viewpoints. Scales, like items of length measurement or objects of known size, are often used in the picture so that dimensions of items are recorded on the image.
Crime or accident scene photographers usually capture images in color
but also in black and white
. The photograph of the skid mark
was made during reconstruction at the accident scene to show how and why the ladder
had slipped and caused a serious injury to the user. Color pictures are generally preferred because color may be an important aspect of the trace evidence
, for example. Thus traces of paint
or dye
on a piece of evidence may be crucial to linking the evidence with a crime or accident.
Various forces and different countries have different policies in regards to 35 mm film
or digital photography
. There are advantages and disadvantages to both. Conventional film photographs, even using disposable camera
s, have a high resolution, enabling great enlargement should details in a picture need closer examination. Pictures from surveillance cameras are a growing source of evidence for courts, as are pictures taken by bystanders on mobile phone
s. The former are being used increasingly at accident blackspot
s, and bystanders may take pictures of events when no police officer or investigator is present, but yet may be critical to a case. Digital photographs usually have an automatic date and time marker on each image, so that authenticity can be verified. Conventional photographs without such marks must be authenticated by the photographer, usually in a witness statement
. Pictures of the relative position of objects (as in a Palimpsest
) can establish a sequence of events at a crime
or accident scene. Due to continued advances in digital technology and software, digital single-lens reflex (DSLR) cameras are increasingly being used by law enforcement agencies.
The images must be clear and usually have scales. They serve to not only remind investigators of the scene, but also to provide a tangible image for the court to better enable them to understand what happened. The use of several views taken from different angles helps to minimise the problem of parallax
. Overall images do not have scales and serve to show the general layout, such as the house where the murder is thought to have occurred. Context images show evidence in context, like how the knife was next to the sofa. Close up images show fine detail of an artifact, such as a bloody fingerprint on the knife.
Road traffic incident (RTI) photographs show the overall layout at the scene taken from many different angles, with close-ups of significant damage, or trace evidence
such as tire marks at a traffic collision. As with crime scene photography, it is essential that the site is pristine and untouched as far as is possible. Some essential intervention, such as rescuing a trapped victim, must be recorded in the notes made at the time by the photographer, so that the authenticity of the photographs can be verified.
As with all evidence a chain of custody
must be maintained for crime scene photographs. Sometimes a CSI (forensic photographer) will process his/her own film or there is a specific lab for it. Regardless of how it is done any person who handles the evidence must be recorded. Secure Digital Forensic Imaging methods may be applied to help ensure against tampering and improper disclosure. Accident scene pictures should also be identified and sourced, police photographs taken at the scene often being used in civil cases.
Crime or accident scene photographs can often be re-analysed in cold cases or when the images need to be enlarged to show critical details. Photographs made by film exposure usually contain much information which may be crucial long after the photograph was taken. They can readily be digitised by scanning, and then enlarged to show the detail needed for new analysis. For example, controversy has raged for a number of years over the cause of the Tay Bridge disaster
of 1879 when a half-mile section of the new bridge collapsed in a storm, taking an express train down into the estuary of the river Tay. At least 75 passengers and crew were killed in the disaster.
The set of photographs taken a few days after the accident have been re-analysed in 1999-2000 by digitising them and enlarging the files to show critical details. The originals were of very high resolution since a large plate camera was used with a small aperture
, plus a small grain film. The re-analysed pictures shed new light on why the bridge fell, suggesting that design flaws and defects in the cast iron
columns which supported the centre section led directly to the catastrophic failure
. Alternative explanations that the bridge was blown down by the wind during the storm that night, or that the train derailed and hit the girders are unlikely. The re-analysis supports the original court of inquiry conclusions, which stated that the bridge was "badly designed, badly built and badly maintained".
Crime scene
A crime scene is a location where an illegal act took place, and comprises the area from which most of the physical evidence is retrieved by trained law enforcement personnel, crime scene investigators or in rare circumstances, forensic scientists....
or an accident
Accident
An accident or mishap is an unforeseen and unplanned event or circumstance, often with lack of intention or necessity. It implies a generally negative outcome which may have been avoided or prevented had circumstances leading up to the accident been recognized, and acted upon, prior to its...
scene using photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
for the benefit of a court or to aid in an investigation. It is part of the process of evidence
Evidence (law)
The law of evidence encompasses the rules and legal principles that govern the proof of facts in a legal proceeding. These rules determine what evidence can be considered by the trier of fact in reaching its decision and, sometimes, the weight that may be given to that evidence...
collecting. It provides investigators with photos of victims, places and items involved in the crime. Pictures of accidents show broken machinery, or a car crash, and so on. Photography of this kind involves choosing correct lighting
Photographic lighting
Photographic lighting is the illumination of scenes to be photographed. A photograph simply records patterns of light, colour, and shade; lighting is all-important in controlling the image. In many cases even illumination is desired to give an accurate rendition of the scene. In other cases the...
, accurate angling of lenses
Photographic lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...
, and a collection of different viewpoints. Scales, like items of length measurement or objects of known size, are often used in the picture so that dimensions of items are recorded on the image.
Methods
Color photography
Color photography is photography that uses media capable of representing colors, which are traditionally produced chemically during the photographic processing phase...
but also in black and white
Monochrome photography
Monochrome photography is photography where the image produced has a single hue, rather than recording the colours of the object that was photographed. It includes all forms of black-and-white photography, which produce images containing tones of grey ranging from black to white. Most modern...
. The photograph of the skid mark
Skid mark
A skid mark is the mark a tire makes when a vehicle wheel stops rolling and slides or spins on the surface of the road. More generally, any solid which moves against another can cause visible marks, and is an important aspect of trace evidence analysis in forensic science and forensic engineering...
was made during reconstruction at the accident scene to show how and why the ladder
Ladder
A ladder is a vertical or inclined set of rungs or steps. There are two types: rigid ladders that can be leaned against a vertical surface such as a wall, and rope ladders that are hung from the top. The vertical members of a rigid ladder are called stringers or stiles . Rigid ladders are usually...
had slipped and caused a serious injury to the user. Color pictures are generally preferred because color may be an important aspect of the trace evidence
Trace evidence
Trace evidence is evidence that occurs when different objects contact one another. Such materials are often transferred by heat induced by contact friction....
, for example. Thus traces of paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
or dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
on a piece of evidence may be crucial to linking the evidence with a crime or accident.
Various forces and different countries have different policies in regards to 35 mm film
35 mm film
35 mm film is the film gauge most commonly used for chemical still photography and motion pictures. The name of the gauge refers to the width of the photographic film, which consists of strips 35 millimeters in width...
or digital photography
Digital photography
Digital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...
. There are advantages and disadvantages to both. Conventional film photographs, even using disposable camera
Disposable camera
The disposable or single-use camera is a simple box camera sold with a roll of film installed, meant to be used once. Most use fixed-focus lenses. Some are equipped with an integrated flash unit, and there are even waterproof versions for underwater photography...
s, have a high resolution, enabling great enlargement should details in a picture need closer examination. Pictures from surveillance cameras are a growing source of evidence for courts, as are pictures taken by bystanders on mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s. The former are being used increasingly at accident blackspot
Accident blackspot
An accident blackspot is a term used in road safety management to denote a place where road traffic accidents have historically been concentrated...
s, and bystanders may take pictures of events when no police officer or investigator is present, but yet may be critical to a case. Digital photographs usually have an automatic date and time marker on each image, so that authenticity can be verified. Conventional photographs without such marks must be authenticated by the photographer, usually in a witness statement
Witness statement
A witness statement is a statement summarising the oral evidence that a witness will give at trial. The purpose the witness statement is to set out the evidence of the witness; in some jurisdictions the statement will stand as the evidence in chief of the witness , and the trial will simply...
. Pictures of the relative position of objects (as in a Palimpsest
Palimpsest
A palimpsest is a manuscript page from a scroll or book from which the text has been scraped off and which can be used again. The word "palimpsest" comes through Latin palimpsēstus from Ancient Greek παλίμψηστος originally compounded from πάλιν and ψάω literally meaning “scraped...
) can establish a sequence of events at a crime
Crime scene
A crime scene is a location where an illegal act took place, and comprises the area from which most of the physical evidence is retrieved by trained law enforcement personnel, crime scene investigators or in rare circumstances, forensic scientists....
or accident scene. Due to continued advances in digital technology and software, digital single-lens reflex (DSLR) cameras are increasingly being used by law enforcement agencies.
Fit for court
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...
. Overall images do not have scales and serve to show the general layout, such as the house where the murder is thought to have occurred. Context images show evidence in context, like how the knife was next to the sofa. Close up images show fine detail of an artifact, such as a bloody fingerprint on the knife.
Road traffic incident (RTI) photographs show the overall layout at the scene taken from many different angles, with close-ups of significant damage, or trace evidence
Trace evidence
Trace evidence is evidence that occurs when different objects contact one another. Such materials are often transferred by heat induced by contact friction....
such as tire marks at a traffic collision. As with crime scene photography, it is essential that the site is pristine and untouched as far as is possible. Some essential intervention, such as rescuing a trapped victim, must be recorded in the notes made at the time by the photographer, so that the authenticity of the photographs can be verified.
As with all evidence a chain of custody
Chain of custody
Chain of custody refers to the chronological documentation or paper trail, showing the seizure, custody, control, transfer, analysis, and disposition of evidence, physical or electronic...
must be maintained for crime scene photographs. Sometimes a CSI (forensic photographer) will process his/her own film or there is a specific lab for it. Regardless of how it is done any person who handles the evidence must be recorded. Secure Digital Forensic Imaging methods may be applied to help ensure against tampering and improper disclosure. Accident scene pictures should also be identified and sourced, police photographs taken at the scene often being used in civil cases.
Analysis of historic photographs
Tay Bridge disaster
The Tay Bridge disaster occurred on 28 December 1879, when the first Tay Rail Bridge, which crossed the Firth of Tay between Dundee and Wormit in Scotland, collapsed during a violent storm while a train was passing over it. The bridge was designed by the noted railway engineer Sir Thomas Bouch,...
of 1879 when a half-mile section of the new bridge collapsed in a storm, taking an express train down into the estuary of the river Tay. At least 75 passengers and crew were killed in the disaster.
The set of photographs taken a few days after the accident have been re-analysed in 1999-2000 by digitising them and enlarging the files to show critical details. The originals were of very high resolution since a large plate camera was used with a small aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
, plus a small grain film. The re-analysed pictures shed new light on why the bridge fell, suggesting that design flaws and defects in the cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...
columns which supported the centre section led directly to the catastrophic failure
Catastrophic failure
A catastrophic failure is a sudden and total failure of some system from which recovery is impossible. Catastrophic failures often lead to cascading systems failure....
. Alternative explanations that the bridge was blown down by the wind during the storm that night, or that the train derailed and hit the girders are unlikely. The re-analysis supports the original court of inquiry conclusions, which stated that the bridge was "badly designed, badly built and badly maintained".
See also
- Forensic engineeringForensic engineeringForensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability. The field also deals with...
- Forensic materials engineeringForensic materials engineeringA branch of Forensic engineering, the subject focuses on the material evidence from crime or accident scenes, seeking defects in those materials which might explain why an accident occurred, or the source of a specific material to identify a criminal...
- Forensic polymer engineeringForensic polymer engineeringThe study of failure in polymeric products is called forensic polymer engineering. The topic includes the fracture of plastic products, or any other reason why such a product fails in service, or fails to meet its specification...
- Forensic science
- PhotographyPhotographyPhotography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
- History of forensic photographyHistory of forensic photographyForensic science holds the branch of Forensic photography which encompasses documenting both suspected and convicted criminals, and also the crime scenes, victims, and other evidence needed to make a conviction...
- Skid markSkid markA skid mark is the mark a tire makes when a vehicle wheel stops rolling and slides or spins on the surface of the road. More generally, any solid which moves against another can cause visible marks, and is an important aspect of trace evidence analysis in forensic science and forensic engineering...
- Trace evidenceTrace evidenceTrace evidence is evidence that occurs when different objects contact one another. Such materials are often transferred by heat induced by contact friction....