Sure would like to see a copy of the warrant...
I think this helps the defense. They can work to get this cleared up (find out why the warrant was issued, get the facts concerning the 2003 case) before putting Mostafa on the stand so that Mostafa's credibility will not be impeached.
Both the defense and prosecution will run checks on their witnesses because they don't want any surprises to come out at trial. The defense has been handed a gift because they can now rehabilitate Mostafa and won't be blindsided at trial by the 2003 warrant.