A secular court and 12 jurors of one’s peers has no neemanus or believability or acceptability in halacha or Judaism. NW status to us remains the same as it was before the DA or court acted.
And, in your eyes, Levi Aron is not a murderer, since he was only convicted in a secular court.*
The Wolf
* And, before you point out that he confessed, let’s remind you that criminal confessions are completely disregarded under Jewish law.