Digital Cameras Using Infrared Radiation

Mark Burry, W. Jerry Chisum, Dusty Clark-Calif.Dept. of Justice, Bureau of Forensic Services

Infrared?  Digital Cameras? 

IR radiation is a spectrum of electromagnetic waves that are longer than visible light and shorter than radar.

DIGITAL CAMERAS, vastly simplified, are devices that capture images into computer memory rather than on film.

A Brief history of IR Photography:  It began over 35 years ago and involved 1) long exposure times, and 2)impractical handling, usage, and development of  IR film.  It was effective but inefficient.

Along came O. J. 's socks:  Dusty Clark used infrared video to document blood stains on the black socks. If it worked with video did it work with digital cameras? 

The experiments:  Using the Kodak DCS 420 digital camera for IR photography on: 1) Gunshot powder patterns, 2)Powder patterns under bloodstains, 3)Bloodstains of different dilutions.

Gunshot Powder Patterns:  What was done.  1) Fired a .38 special cartridge through various fabrics using a .357 S&W revolver at a distance of 3-4 inches, and 2) Photographed the powder patterns with and without an IR filter.

        No Filter                  Black  Wool              IR Filter  

        No Filter                Printed Fabric            IR Filter

Powder Patterns under blood stains-what was done: 1)  Covered halves of the previous tests with blood, 2) Photographed them with and without the IR filter .

        No Filter                Black Wool                IR Filter

       No Filter                Printed Fabric             IR Filter

Blood Stains of Different Dilutions

Blood was serially diluted out to 1:32 and placed onto dark wool fabric and photographed with and without the IR filter.  Blood was barely visible at 1:16 and could be said to be visible in IR at 1:8 dilution.

ADVANTAGES OF DIGITAL PHOTOGRAPHY IN IR

1) Portable, 2) Instant Results, 3) Doesn't require the use of chemicals to visualize blood, 4) IR is not harmful to DNA, 5) Ease of presentation and visualization,6) Effective and Efficient.

DISADVANTAGES OF IR DIGITAL IMAGING

1) Resolution is lost with distance, 2) Expensive, 3) Less expensive digital cameras have a hot mirror filter which blocks IR from striking the CCD.

      No Filter                       Blood on Blue Jeans                IR Filter

  FFT filter&Enhancement    

CONCLUSION:  Both Blood and GSR were visible at differing levels of IR reflectance and blood was detectable at a dilution of 1:8 ratio.

  ANOTHER REASON MAKE THE MOVE TO DIGITAL CAMERAS