John served as an investigative consultant for ABC World News I-Team based in Miami. After working for John became an reporter for WAMI TV in Miami. His investigations included uncovering a multi-million dollar kickback scheme at Miami International Airport, legal loan sharking in the auto title loan business, and financial ties between a local mayor and organized crime. From there, John became the investigative reporter for the nationally syndicated Uncovered TV in Los Angeles. More recently, he has been reporting from San Diego. His reporting has earned him 6 Emmys, an Edward R Murrow Award, a Golden Mike and 10 Press Club awards.
Mattes in 2009 founded InvestigativeGuy.com, an online site dedicated to defending consumers and exposing scams and fraud.