It sounds like he has backlinks on sites that are not indexed. Why are these sites not indexed? There could be a few reasons
a) brand new site, in that case they won't be passing PR once indexed but you might as well try to get them indexed by adding the URL to googles addurl tool which tells google to spider the site
b) links are on pages that are blocked from bots or noindex. in that case they are useless for SEO
c) site was banned from Google. If a site used to be indexed and is not deindexed not by the owner but by Google you want to get your links off of those pages because you could get penalized as a result