A study published in Forensic Science International has examined how brain scans can be of use to forensic pathologists – clinicians who perform autopsies to better understand how someone has died, often to provide evidence for a criminal investigation.
These cases will typically involve a police investigation, and the usual method is for a forensic pathologist to perform an autopsy on the head and brain to establish exactly what sort of injury occurred.
One of the drawbacks of this method is that it can only be performed once. The tissue is dissected and it’s not possible to keep anything except small samples.
This can be a problem in court, because it means the pathology evidence largely rests on a single examination, done in whatever way the pathologist thought was best, and can rely on their subjective interpretation.
A brain scan might be useful in this situation as it could be independently assessed and might actually pick up some things which might otherwise be missed if the head has to be dissected to be examined.
The study, led by Dr Kathrin Yen, compared findings from a structural MRI scan, a CT scan (an older structural brain scanning technique that uses X-rays) and a post-mortem, on 57 people, the majority of whom had died from serious head injury.
The findings from the scans and the autopsies were compared to see how well they agreed with each other.
The examination of the brain scans entirely missed some signs, such as increased brain pressure, but was 100% accurate in others, such as detecting bleeds between the dura mater, the brain’s tough outer membrane, and the skull.
The researchers note that some of the poor results are likely to be because radiologists aren’t used to forensic examinations as they’re trained to examine living people.
However, the brain scans had a distinct advantage in some cases. In one instance, the brain scan better estimated the size of an internal bleed which was exaggerated during autopsy because it bled further as the brain was cut.
The brain scans also allowed 3D reconstructions which could be examined from various angles to better understand how impacts occurred or what sequence of events might have caused the damage.
The image on the left is of a heat-induced fracture in a man who died in an aeroplane crash. The scan allows the pathologist to see the relationship between the skull fractures and the bleeds in the brain from a number of angles.
The study suggests that brain scanning corpses may give important clues in a forensic investigation but that radiologists may need to be specially trained so they know what they’re looking for.