Science - Photograph / image analysis experts

Introduction

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 a recommendation 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.

Sample Reports

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.

Cost

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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