What does a bruise look like

How do you know how old a bruise is?

A bruise can be many colors. For coroners, knowledge is essential in helping solve crimes.

Not paying attention for a moment, and suddenly the door frame was in the way. Or the edge of the table. And already a bruise forms, as it is popularly known. "Bruises are soft tissue injuries and are caused by blunt force, such as a fall or blow," says Kathrin Ogris from the Institute for Forensic Medicine in Graz. Blood enters the surrounding tissue - usually the subcutaneous fatty tissue - without damaging the overlying skin. Because in order to be visible at all, the blood has to collect close to the surface. Deep-seated hematomas are sometimes not discovered at all or only bloom some time later.

When blood is broken down, a biochemical process happens in the body: the hemoglobin responsible for the red pigment in the red blood cells changes until it finally disappears completely. Until then, however, the spots take on different colors: they are greenish after about four to five days, yellowish after about eight days. There are also many shades in blue and brown tones.

Inferring the time of the crime

How the color gradient develops and how quickly the spots disappear again differs from person to person: the blood vessels of older people tear more easily and also have less protective fatty tissue than younger ones.

The weaker connective tissue makes it easier for women to bruise than men. But injuries can also develop differently in one and the same person, for example having different colors even though they are the same age.

Understanding how hematomas develop is important in forensic medicine because it allows conclusions to be drawn about the time of the crime, such as child abuse or another crime. “We always have to look into the past to understand how an injury occurred,” said Ogris. Clinically irrelevant findings such as bruises, which usually do not require any therapy, can also be decisive. The “gold standard” is still to look at the injuries externally and evaluate them using a color scale. Although this is not a very exact one, it is still the best way to determine the age at the moment.

Ogris wants to understand her better in her work, for which she also conducts research at the Ludwig Boltzmann Institute for Clinical Forensic Imaging. To do this, she artificially applied hematomas to healthy adults in a study: she injected blood from the arm vein into the thigh. She documented the changes with photos, but also looked inside her subjects with magnetic resonance imaging.

The result: the color gradient was very variable. “Very few of the hematomas looked the same, which shows how many different influences are at work,” says Ogris. With her research, she showed that an objective assessment of the point in time of development is possible using imaging. She now wants to pick up on this: because an artificially placed hematoma does not correspond to the consequences of blunt force, she inflicts small bruises on the test subjects with a mechanical device.

Incidentally, all of them have volunteered for science - and also receive a small allowance.

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[MKLQU]

(Print edition, July 23, 2016)