so what if he did prior knowledge .charge him with whatever you think you can .doesnt alter much for jb 
The only thing that has the slightest chance of ever setting Jeremy free is the truth,the whole truth and nothing but the truth.
If Jeremy had said a couple of things to Brett about killing his parents and Brett had thought Jeremy wasn't serious - then Brett would hardly be to blame for the actual murders ...
But what if Brett had killed someone before in a robbery like Susan Battersby says in her statement - and then he met a naive teenage Jeremy with rich parents - and then encouraged or persuaded Jeremy to do it so he could spend the inheritance money with Jeremy - that would make Brett a child killer.
If it ever turned out that Jeremy had been seriously manipulated or seriously threatened by an older criminal to commit the murders then it would create a very slight possibility for Jeremy to seek reconsideration of his whole life tarrif.
Only the truth has a chance of ever setting Jeremy Bamber free.
What is the truth in this case ?