I don't know what Julie committing minor cheque book fraud with Susan Battersby as a 19 year old in 1984 , has got to do with Bamber massacring his family. Apart from it would deter Julie from approaching the police after the massacre, as Bamber knew about the cheque book fraud.
Ditto the caravan break in which Bamber got Julie to be a look out. Julie told the police about the caravan break in. The judge also said that the caravan break in showed Bamber trusted Julie enough to involve him in his crimes.