"To justify this claim" means to provide reasons, evidence, or explanations that support a statement or argument, in order to prove or vindicate it. Full definition
By the same token, injury alone does not justify a claim of malpractice. (clufflaw.com)
He could have claimed more if he had organised his affairs differently, but that does not justify a claim outside the rules. (nextleft.org)
This part of writing a CV should include notable organizations and award - giving bodies that will surely impress the hiring officer and that will justify your claims in the qualification statement. (resumewritingservice.biz)