What we know and don't know Justin DuMorne; and what we may assume about him.
Maggie tried to get Ebenezer to join in an unknown (to us) scheme with Duchess Arianna and Lord Raith. Justin DuMorne was also one of her associates. However, we don't know if Justin was associated with Margaret LeFey at the same time she was working with Lord Raith. She could have made different allies at different times and in different circumstances.
Justin removed Harry from an orphanage shortly after Harry's magic ability started to emerge. We can assume something similar for Elaine, but we don't know for certain. There might be important differences in how and why Justin selected each of them, but we have nothing to confirm this possibility.
We can assume Justin wasn't on the run from the White Council when he adopted Harry and Elaine. If he had been on the run it seems unlikely he could live in one place very long with any degree of safety and raise two teenagers at the same time. From this we can also assume that whatever his true relationship was to Harry's mother, from the White Council's perspective it couldn't have looked nefarious, at least as long as they didn't look too closely. Many wizards must have known Margaret before she had broken any of the Laws of Magic, and Justin might have claimed that he hadn't been in contact with her after she went rogue, even if that wasn't true.
HWWB knew Justin DuMorne or knew enough about him to drop his name when the Walker was talking to Harry the first time they met. Harry assumed Justin called HWWB behind to go after Harry after he ran away. That was a logical assumption for Harry to make, but we don't know with certainty if this was the case.
We don't know how the events played out that lead to Justin's death. (Assuming he did in fact die.) The early books are a little vague on the details. We know Elaine hit Harry with a binding that he was eventually able to break. There was also an attempt to force Harry to drink human blood in some type of ritual which we can assume would have enthralled Harry to Justin's will. Elaine was chanting and her body was painted with swirling patterns which seems to confirm that a ritual was being used. At some point Harry is free and all we really know is Harry vividly remembers seeing Justin burn to death and that he continued to watch Justin's corpse blacken and shrivel in the flames.
That's about it other than other people and not people's opinions of Justin. Ebenezer called Justin a "son of a bitch." Bob told Harry that Justin got what he deserved. Lea told Harry that he wanted to give Justin the benefit of the doubt, but he was wrong to do so; in other words Justin got what he deserved. From this, all we can really be certain of is that Lea didn't tell Harry a direct lie about Justin. There may have been, and probably was much she didn't tell Harry about Justin, because Harry was only drawing upon his own memories of Justin, Lea wasn't sharing any of hers. I suppose we can also trust Bob's opinion because he didn't have any reason to lie to Harry, but Bob doesn't have a strong grasp of morality so his opinion on when it's right to kill someone can be somewhat shaky. We really don't know when and how Ebenezer formed his opinion of Justin.
There is one last tiny bit of information which possibly links Justin to Lea. From time to time young Harry was visited by a beautiful women with red hair when he was at the orphanage, Lea. (I don't remember which book Harry had this memory in.) It's easy to assume Lea was simply fulfilling her bargain with Margaret to look after Harry, but she was probably also there to check if Harry's magic had stated to manifest. She could have detected magic far more easily than any mortal could have. This also could have also been part of her bargain with Margaret, Lea might have agreed to find someone to teach Harry how to use magic, but Lea might also have made a separate agreement with Justin. There is a huge gap in our knowledge here.
I'm hoping Peace Talks will give us more information about Margaret LeFay and by extension Justin DuMorne.
