Given the proliferation of digital photography since the introduction of smart phones with high-resolution CCD sensors around 2006, legal trials increasingly rely on images in the presentation of evidence. Cameras and storage costs are so affordable now that people can install CCTV cameras in their own house and even have ‘dash cams’ in their vehicles recording their commutes in the event of a collision, in order to assign blame. It is common for motorbike and bicycle riders to record video from their helmets in order to record traffic infringements against them. People have quickly become conditioned to take photographs or videos if an event occurs that may have legal consequences, such as antisocial behaviour in public, suspicious behaviour (e.g. loitering, etc) or a traffic collision or workplace accident.
However as an added degree of complication, it is also increasingly easy to manipulate photographs, either as they are taken (via filters, AI image processing software) or afterwards via popular software such as Photoshop and Lightroom. Software on mobile phones can instantly ‘beautify’ a subject or add overlays, remove background objects, change the sky, or merge two or more photographs together, requiring no training or expertise from the photographer.
Consequently, police detectives and legal authorities are increasingly requiring photographic and video still images to be verified by experts in photograph and image analysis. Such experts rely on a detailed knowledge of the “image pipeline” from the CCD sensor to the final digital file in order to inspect and verify images. The process is analogous to ballistics in determining if a bullet came from a certain firearm.
This image pipeline is often broken down into six key areas:
- Physics: shadows, lighting and reflections
- Geometry: vanishing points, distances within the image and 3D models
- Optical: lens distortion, chromatic aberration, inconsistent focus and bokeh
- Image Sensor: fixed pattern noise and colour filter defects. It helps if the forensic expert has access to the camera that supposedly took the photograph, or at least the camera model so that the same imaging characteristics can be independently verified.
- File format: metadata, file compression, thumbnails and EXIF and GPS markers
- Pixel: scaling, cropping, cloned or resaving
Some of these principles will also apply to traditional analogous photography using film and wet developing. Just as there are automated image-manipulation tools, increasingly there are automated imagine-manipulation detection tools, such as algorithms that detect if areas of the photograph have been copied, erased or replaced. Facial recognition, based on geometrical proportions is another process that can be automated. Going forward, this “arms race” between manipulation and detection is set to continue and expand into the use of video footage.
At the bottom of this profile are brief details of a number of the experts that Expert Experts represents. Call our office to discuss your requirements and to obtain an expert submission that suits your needs and budget.
Expertise in Action
Experts in photograph / image analysis will be required to give their opinions in cases where photographic evidence is disputed e.g. it is alleged that an image has been manipulated to disguise or shift culpability. In addition, forensic examination of photographs and their underlying digital data may assist investigators in determining the time of day or location.
For some fields of expertise we have some sample sections of de-identified reports. Please contact our office if you are interested in a sample.
The overall cost of expert opinion depends on the services required. Some of the key factors that affect the cost of advice include:
- The need for a view or inspection of a location
- The quantity of documentary material to be reviewed
- Whether there are reports of other experts to be reviewed and commented on in detail
- Whether there is a need for conferences with the expert either in person or by telephone/Skype
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Looking and knowing: Jurors and photographic evidence
Courts are now accepting expert evidence using new technological methods for ‘reading’ photographs. New technologies produce new ways of seeing. These technologies purport to mediate between the juror and the image, rendering legible, or visible, what was previously unclear. These techniques are supposed to narrow the gap between 'resemblance' and ‘recognition’. They are supposed to assist the jury to make a better determination of the facts.
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The Reliability of CCTV Images as Forensic Evidence
Forensic evidence originating from CCTV images is admitted as evidence into
various criminal courts in Australia and overseas. It is used predominately to identify
persons of interest from images captured by CCTV cameras but other forms of
forensic evidence and intelligence are also possible. Using a mixed method research
design, this study examines the reliability of CCTV images when used as forensic
evidence. A range of strategies including case studies, empirical experimentation and
phenomenological inquiry is used to investigate the application of this new form of
evidence. Understanding the reliability of evidence derived from photographic
sources requires a highly complex interdisciplinary and multifaceted approach. This
study has found serious reliability problems with the current use of CCTV images
when used as forensic evidence. Serious miscarriages of justice are inevitable if the
reliability of photographic evidence practices are not more carefully considered and
Wood v State of New South Wales  NSWSC 1247
The date and timing of photographs used as evidence as to where Caroline Byrne’s body was located at the base of The Gap, a matter that was crucial to differentiating between murder and suicide.
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