Bruise Clock

Red on the first day, purple by the third, then green and yellow. The sequence is familiar, and it will not tell you when a bruise was inflicted.¹

Child protection cases have turned on that reading, and the evidence does not support it.¹

Sabine Maguire and colleagues at Cardiff University tested the practice directly.¹ Their systematic review, published in Archives of Disease in Childhood in 2005, examined 167 studies; three met the criteria for inclusion, two assessing bruise colour in living children and one working from photographs.¹ What those studies showed was that any colour could be present in a bruise that was fresh, intermediate or old.¹ Reports on when yellow first appears contradicted one another.¹

The figures on clinician performance are the part worth holding onto. Asked to date a bruise to within twenty-four hours, clinicians were correct less than 40 per cent of the time.¹ Asked for the easier judgement of whether a bruise was fresh, intermediate or old, they were correct between 55 and 63 per cent of the time.¹ Agreement between observers was poor, and so was agreement between the same observer on separate occasions.¹ The authors concluded that estimating the age of a bruise from its colour has no scientific basis and should be avoided in child protection proceedings.¹

That conclusion has held. The Royal College of Paediatrics and Child Health carries the review in its Child Protection Evidence series, published in March 2020 on a literature search running to January 2019, and states that a bruise cannot be accurately aged by looking at its colour.² It also records that clinicians continue to be asked to do it, and advises checking current literature and taking local specialist advice in any individual case.²

The reason the practice persists is that it is useful. An estimated hour of injury turns a photograph into evidence and closes a gap in a timeline. That is precisely the circumstance in which a confident number does the most harm.