And maybe there's no evidence because he didn't have any mental health issues.
The Bamber family of 4 was created by adoption with SC and JB hailing from different birth families ie no shared genes. June and SC had long histories of mental illness. 2 out of 4 is statistically unusually. What would be the chances of 3 out of 4? I believe the stats show 1 person in 4 will suffer a mental health issue every year. In the Bamber family we have a concentrated cluster at 2 out of 4 let alone 3 out of 4. Either way the stats suggest there's something more at play here. Especially given the Bambers were very much middle class ie not tearing their hair out wondering how they're going to fund the elec. meter and divide a can of beans 4 ways.
You may -or not- recall that I've previously wondered what were the chances of adopting two genetically unrelated children who both become afflicted with forms of mental illness/personality disorders, albeit, I'm aware that a PD isn't a mental illness. It comes as no surprise to me. It may not have been so much about the Bambers attempting to slot them into holes which didn't fit their personalities, so much as them feeling they HAD to force themselves into those holes, possibly resulting in neither of them knowing who they were and where they fitted.
If there is no evidence of Jeremy having any kind of mental abnormality/brain injury, it seems strange that he hasn't produced the evidence as a way of silencing those who say the crime was committed because of such. Surely it would be in his favour?