Visual assessment of the timing of bruising by forensic experts

Forensic experts are frequently asked to comment on the age of injuries and interpretation may have significant medico-legal consequences. The purpose of this study is to determine the accuracy with which forensic experts can visually age a bruise from photographs produced under standard conditions.

Bruises were produced on the upper arms of 11 subjects by a suction pump. Sequential photographs were taken daily until they were no longer visible to the naked eye. Fifteen forensic experts who did not know the age of the bruises were asked to estimate their ages and also to place them in chronological order.

Hundred and thirty-two images of 25 bruises were produced, ranging from 0 to 209h in age. There was considerable inter- and intra-observer variability in accuracy (median difference between the estimated age and the real age=26.0h (95% C.I. 24.0-31.0h). There was greatest accuracy for bruises photographed between 0 and 12h. No significant differences were seen between male and female observers (p=0.553) and performance was also unaffected by the age of the observer (p=0.160). Of the bruise images placed in chronological order >80% of the observers made between 0 and 2 errors.

Bruise age estimates by forensic experts, from photographs, are unreliable. However, it appears that the vast majority of observers are better able to place bruises from the same subjects in their chronological order.