Detection of Latent Bloodstains Beneath Painted Surfaces Using Reflected Infrared Photography

Abstract

Bloodstain evidence is a highly valued form of physical evidence commonly found at scenes involving violent crimes. However, painting over bloodstains will often conceal this type of evidence. There is limited research in the scientific literature that describes methods of detecting painted-over bloodstains. This project employed a modified digital single-lens reflex camera to investigate the effectiveness of infrared (IR) photography in detecting latent bloodstain evidence beneath a layer or multiple layers of paint. A qualitative evaluation was completed by comparing images taken of a series of samples using both IR and standard (visible light) photography. Further quantitative image analysis was used to verify the findings. Results from this project indicate that bloodstain evidence can be detected beneath up to six layers of paint using reflected IR; however, the results vary depending on the characteristics of the paint. This technique provides crime scene specialists with a new field method to assist in locating, visualizing, and documenting painted-over bloodstain evidence.

Use of an Alternate Light Source to Detect Tooth and Bone

“…ROIs are areas in the same size, selected and cut with Photoshop in the same positions in all the samples to maintain a standard in the analysis of the measurements. These ROIs were transformed into 8-bit/channel "grayscale" images, so that the color information could be discarded, to maintain consistency during the analyses (13). The obtained images were saved in TIFF format.…”

Simplified digital infra red photography: an alternative tool in Bite mark forensic investigation

“…If your camera is capable of autofocusing in low light down to exposure compensation 0 (EV0) or not much above, you'll be just fine. 12,32 Other inferiority of digital SLRs in IR photography in autofocusing is because the AF is done by dedicated sensors behind a system of mirrors. These sensors are at the same effective distance from the lens as the imager.…”

“…If you have a ring flash, just attaches it on the flash unit screw in and bring it tightly closed to the lens after focusing, but it must be sure that no visible light enters. 6,32 …”

“…Other wavelengths of light strike the skin and diffuse throughout the layers of the skin such that they dissipate without being absorbed or reflected. 1,5,10 One final event that occurs when light strikes skin is a molecular-level excitation within the skin that increases the resting state energy of the molecules within the skin, which is known as biofluoresence. Almost anything can be made to fluorescence.…”

“…IR also has the ability to see through blood. 10,27,28 With practice, the forensic photographer should be able to repeatedly get good results using the IR technique.…”