Blood - Detection, Identification & Age Determination

Haemoglobin is the protein responsible for oxygen transport in the blood, making up 97% of the blood's dry content. Upon contact, with oxygen outside the body, haemoglobin will convert to three consecutive derivatives over time; oxyhaemoglobin (HbO2) --> methaemoglobin (MetHb) --> hemichrome (HC). Fresh to old blood - colour change over timeThis transition is accompanied by a colour change over time from deep red to dark brown, as is illustrated in the image on the right.

The colour change of the blood is caused by the different optical properties of the haemoglobine derivatives. The bright red HbO2 transforms into the dark red MetHb and into the dark brown HC. With reflectance spectroscopy techniques the amount of each of the derivatives in the bloodstain can be established. Based on the measured spectra it is possible to detect and identify blood stains at the crime scene, and above all the age of the bloodstain can be determined. The possibility to determine the age of a blood stain is one of the unique technologies that is developed by the researchers of FTS.

There are several possibilities to determine the spectra of the blood stains. The two main groups are demonstrated in the following images.

Reflectance Spectroscopy

 

Reflectance spectroscopy is a fiber based measurement technique. White light is directed onto the sample where it is partially absorbed and reflected. The reflected light is directed to the spectrometer where the reflection spectrum of the sample is determined. This spectrum is the output of the measurement. With these so called point measurements no additional information of the sample, e.g. its location or form, is obtained. This, however, is possible with spectral imaging, a combination of spectroscopy and digital imaging. By using a panoramic line-scanning method an image with spectral information is obtained. For every pixel in the image a spectrum is acquired which can be used for further analysis; detection, identification and age determination of blood.

Spectral Imaging

 

By using reflectance spectroscopy and spectal imaging the detection, identification and age determination of blood stains can be accomplished without touching or destroying the sample. Due to the small components the systems are portable and perfectly applicable in the lab as well as at a remote location. It is therefor ideal for measurements in a forensic setting. The measurements can take place at the crime scene without the risk of contamination or destruction of the traces.

 

Forensic Technical Solutions B.V.

Meibergdreef 45 - 1105 BA Amsterdam - The Netherlands - info@fortechs.com - (+31) (0)20-2050911