Imagine you're a social worker evaluating a claim of child abuse. The child has no broken bones and no bruises. But the case isn't simply a "he said, she said" affair. As a final check you have the child sit on a special chair in a tube with her head in a bracket lined with foam rubber, you walk out of the room, press a button, wait, and enter the e-mail address of a consulting radiologist at a nearby public hospital.
An hour later, a preliminary report comes back in a reply e-mail: "The brain scan indicates that the child has been abused or suffers from chronic depression."
The technology hasn't reached this point yet, but it is getting closer. It is now possible to detect the telltale signs of child abuse in post-mortem examinations of the brains of trauma victims. For CSI and forenic pathology purposes, we are extremely close to being able to include brain tissue evidence along with other more traditional physical signs of child abuse.
The place to look is the hippocampus, which is a brain structure associated with learning and memory, which is part of the limbic system (aka the mammilian brain). One symptom is high levels of methylation in rRNA genes there. Reduced hippocampus volume is also relevant. Child abuse and chronic depression look similar.
The research that revealed the linkage compared the brains of car accident victims with no known history of child abuse with suicide victims known to have a history of child abuse.