New optical technology will help date a persons bruises

Nov 4 2004

Optical technology can give the answer to when bruising happened and how. This can be important for cases of violent crime.

In court, a bruise can sometimes be important evidence. And the age of the bruise can be instrumental if a person is to be charged for the injuries in a crime. A cross-functional research team with the Norwegian University of Scence and Technology (NTNU) is currently developing a method, based on optical technology, for dating bruises. The method will be quick and inexpensive. It does not involve incision in the body, and it would provide a reasonably accurate measurement of bruise’s age.

Today, a bruise’s age is decided by the naked eye. The method is subjective, based on the coroner’s personal knowledge and experience. It is, however, impossible to decide exactly the age of the bruise. The dating will therefore be very approximate. International research shows that coroners date approximately every second bruise incorrectly, and that the margin of error can be up to a week. The bruises are divided into three categories: The fresh that have occured in the last one to two days, bruises that are a “few days old”, and bruising that occured “several days ago”. Technology that is more accurate in determining the age of the skin bruises will in some cases be of importance to the outcome of a trial.

A bruise lasts from one to two weeks. At first it tends to be reddish, then blue-violet, then green, yellow and finally brownish. Researchers use the natural breakdown of the red-coloured material in the blood, haemoglobin, to find the age of the bruise. After a few days, the haemoglobin breaks down into other chemical combinations – that have other colours. “It is the yellow coloured material, bilirubin, that we measure the amount of,” explains project leader Lise Lyngsnes Randeberg at NTNU.

-The naked eye will not perceive this colour until after about two days, while with reflection spectropy we reveal bilirubin after about one day. After about four days the bilirubin amount in the bruise is at its maximum, and afterwards gradually decreases.” The theoretical base for the technology has been developed by Professor Lars Svaasand. The technology is in principle simple: a lamp sends out a white light towards the bruise. White light contains all the colours of the rainbow. The light that reflects from the skin is measured with a spectrometer. More precisely, the spectrometer measures how much of the different colours are reflected back. This will show how far along the bruise has come in its path. From the reflected light, the researchers can measure the amount of blood in the bruise and the oxygen in the blood. Based on these factors, Randeberg is developing an algorithm that will be the key to analysing bruises.

It is possible that bruise technology can be used in several areas. Researchers say that this may come to be used to determine more precisely the time of a victim’s death. International firms in medical technology find this research very interesting, and the team hopes that in a few years the technological results of their work will be common in, among other places, hospital emergency rooms.