Back in March, investigators for controversial Maricopa County Sheriff Joe Arpaio said they had probable cause for believing that President Obama’s long-form birth certificate was computer-generated and faked. Now they say they have proof of the forgery. According to Mike Zullo, Arpaio’s chief investigator, the issue is that numeric codes on certain parts of the birth certificate indicate that those sections were never filled out, yet a section asking for the race of Obama’s father was completed using the identifier “African,” which was not used until 1989, 28 years after Obama was born—indicating, according to Zullo, that someone had tampered with the document. Hawaii state officials refuted Arpaio’s claim on Tuesday, confirming Obama’s citizenship. The White House released Obama’s birth certificate in April 2011, responding to “birthers” who believe that the president was born in Kenya, not Hawaii, and therefore ineligible for office.