A comparison of visible wavelength reflectance hyperspectral imaging and Acid Black 1 for the detection and identification of blood stained fingerprints

Bloodstains are often encountered at scenes of violent crime and have significant forensic
value for criminal investigations.
Blood is one of the most commonly encountered types of biological evidence and is the most
commonly observed fingerprint contaminant. Presumptive tests are used to test blood stain
and blood stained fingerprints are targeted with chemical enhancement methods, such as acid
stains, including Acid Black 1, Acid Violet 17 or Acid Yellow 7. Although these techniques
successfully visualise ridge detail, they are destructive, do not confirm the presence of blood
and can have a negative impact on DNA sampling.
A novel application of visible wavelength hyperspectral imaging (HSI) is used for the non-
contact, non-destructive detection and identification of blood stained fingerprints on white
tiles both before and after wet chemical enhancement using Acid Black 1. The identification
was obtained in a non-contact and non-destructive manner, based on the unique visible
absorption spectrum of haemoglobin between 400 and 680 nm. Results from the exploration
of the selectivity of the setup to detect blood against ten other non-blood protein
contaminants are also presented. A direct comparison of the effectiveness of HSI with
chemical enhancement using Acid Black 1 on white tiles is also presented.