She implicated the other man as JB told her he had arranged a hitman and gave her that name.
I think she believed that statement from him. When it seemed like their relationship was over she might have had good reason to fear that she could be next.....knew too much etc.
I guess she got a lawyer who arranged a deal. ....that she would get immunity in exchange for her evidence, rightly or wrongly that was given.
If JB is innocent (and it would be a terrible MOJ if he is) then it would mean that not just Julie Mugford lied but so did many others. ...AND maintained those lies ever since.
WHY would somebody lie about something so serious as this?
I believe that Julie Mugford told the truth and still believes it to be the truth.
Obviously JB coukd just have been a silly and immature young man making stupid statements about killing his family. He might well have been the arrogant young man he was painted as.....it doesn't make him a killer. But if he did make all those statements.....and then suddenly the family all end up dead, well you'd have to be mad not to have believed he did all he said he was going to.
You just would not lie about that.
Then again...even at that young age when she was equally as immature as JB I find it amazing that she did not speak straight to the police when the family were murdered. I know I would have done.