Complex sentence: While Vialls claims to have been a private investigator for many years, he listed no relevant qualifications, he based most of his investigation on sources that he claimed could not be identified due to their sensitivity, and on information from the media he puported to discredit.
Split into simpler sentences: While Vialls claims to have been a private investigator for many years, he listed no relevant qualifications. He based most of his investigations on sources that he claimed could not be identified due to their sensitivity, and on information from the media he purported to discredit.