Dating yellow bruises
Når fikk han egentlig blåmerket – og hvordan? Optisk teknologi kan gi svaret.
IN A TRIAL, BRUISES may sometimes be important evidence. And the age of the marks could be a decisive factor in deciding whether or not to charge a person in the case. An interdisciplinary research team at NTNU is developing a method of dating bruises using optical technology. This method will be both quick and inexpensive. It does not involve surgery, and is far more accurate than the current technique.
THE NAKED AND SUBJECTIVE EYE
Today, bruises are dated visually, by using the naked eye. This method is subjective, because it is based on the forensic pathologist’s experience and knowledge. However, it is impossible with this technique to determine the exact date when a bruise appeared. This subjective dating is therefore very rough. International studies show that forensic pathologists on average date one out of every two bruises incorrectly, and that the error margin for the date can be as much as one week.
Olav A. Haugen, a forensic pathologist and professor at NTNU, is one of Norway’s experts on dating bruises, and is one of the driving forces behind the interdisciplinary research team. He regularly assists the judicial system with cases where the age of bruises is important. “We divide bruises into three categories: Fresh bruises that have developed within the past 48 hours; marks that are ‘a few days old’, and marks that developed ‘several days ago’,” says Dr. Haugen. He thinks that a technology that can date bruises more accurately will be absolutely crucial to the outcome of at least some trials.
MEASURES REFLECTED LIGHT
Bruises usually disappear within two weeks. At first, a bruise is red, then purplish, blue, green and yellow before turning brown. Researchers use the natural metabolic changes that occur in haemoglobin, a protein that give blood its red colour, to date the mark. As days pass, haemoglobin breaks down into different chemical compounds – each with distinctive colours.
“We measure the amount of the yellow colour substance, bilirubin,” explains Lise Lyngsnes Randeberg, project manager,NTNU.
“The naked eye cannot detect this colour until two days after the mark is made,while reflection spectroscopy reveals bilirubin after one day. The amount of bilirubin reaches a peak after approximately four days, followed by a gradual reduction. The theoretical basis for this technology has been developed by Professor Lars Svaasand.
In principle, the technology is simple: A lamp emits white light towards the bruise. White light consists of all the colours of the rainbow. The light reflected by the skin is measured by a spectrometer,which specifically measures how much of each colour is reflected. This indicates how far the metabolic process has come. Using the reflected light, researchers can record the amount of blood in the bruise and the oxygen level in the blood. Based on these factors, Randeberg is developing an algorithm – the key to interpreting bruise dates.
“Our test subjects were NTNU students with a total of 50 bruises. Most of these marks were caused by sports injuries, such as from martial arts,” says Randeberg.
This part of the study confirmed that it is possible to find traces of yellow bilirubin in bruises before it is visible to the naked eye, and that the development of bruises is fairly similar in young and healthy people. In the autumn of 2004 the research team enlarged their research material by including 150 patients who have undergone heart surgery at St. Olav’s Hospital in Trondheim.
“Bypass operations and angiography cause bleeding under the skin in most patients, a situation that is perfect for this project, because we know to the hour when patients get bruised. Additionally, this is a different age group, so that we can investigate whether age makes a difference in the timing of bruise breakdown. Chief surgeons and associate professors Rune Haaverstad and Rune Wiseth at the Faculty of Medicine,NTNU, will be in charge of this part of the project,” says Randeberg.
The research team will also try to increase their understanding of how injuries may have appeared; how powerful the blow was, and what type of object could have caused the bruise. It is possible the technology of dating bruises can be employed in other areas as well. In the future, researchers think it could be used to more accurately establish the time of death for victims of violence. International medical technology firms find this research very interesting, and the team members hope their work will someday result in this technology being standard in emergency response departments across Norway.
Nina E. Tveter