Digital imaging

Modern digital cameras, computer equipment, and image processing software can be combined to provide significant operational advantages for the capture and enhancement of fingermark evidence. Optimized image capture and the correct application of image processing techniques can result in the recovery of fingermark evidence that may go undetected by other means. The result is that digital imaging has become a viable alternative to conventional photography and a valuable tool for this important forensic application. Chemical imaging further extends the advantages that can be gained through digital capture. Image collection over a wavelength range (hyperspectral imaging), together with the chemometric processing of this data, can result in the significant enhancement of fingermark detail. This is an emerging area that is likely to impact on a number of forensic science disciplines as the technology improves and as the associated equipment costs are reduced. Digital image capture and image processing techniques have, however, resulted in questions being raised as to the validity and acceptability of “photographic” evidence presented in criminal proceedings. Practitioners need to follow standard operating procedures to ensure that acquired images adhere to the same evidential requirements as for other items of evidence. Original digital images must be safeguarded, with any post-capture processing of images only conducted on working copies. In addition, each step in an image processing sequence must be recorded and must be capable of being reproduced (e.g., in court) if questions arise as to the integrity of any image submitted as evidence. What is required is an unbroken “digital image chain of custody” that demonstrates the production of an enhanced image from the original digital recording.