Fontan remains free on bail while awaiting his sentencing on April 28 before U.S. District Judge R. Barclay Surrick.
Assistant U.S. Attorney Neuman Leverett said afterward that he "was happy the jury reached the result they reached."
Fontan met Sanchez in 2003 at the Criminal Justice Center. She was facing drug charges. He said he was a cop and could help her.
He introduced her to two other law-enforcement officers so she could work as an informant. Their relationship became intimate from about 2004 to 2008.
From 2007 to 2008, Fontan joined a Drug Enforcement Administration investigation targeting a Kensington drug dealer, Jose Sanchez, who was Elizabeth Sanchez's ex-boyfriend.
In January 2008, Fontan was asked to make an undercover cocaine buy from Jose Sanchez, but the dealer didn't show up at a planned first-time meeting with Fontan, prompting the feds to wonder if Sanchez was leaked details about the investigation.
Elizabeth Sanchez testified during the trial, saying she never leaked any information to her ex and that Fontan never told her he was investigating her ex. But she admitted she had shown her ex a photo of Fontan on her cellphone in 2006 or 2007.
Fontan's defense lawyer, Jack McMahon, derided the government's charges. For instance, regarding the accusation that Fontan had told Elizabeth Sanchez that Jose Sanchez was indicted on drug charges in July 2008, McMahon said in his closing argument Thursday: "Who cares whether he told her or not?"
He scoffed at the government's focus on a trip to Disney World that Fontan and Elizabeth Sanchez took, saying it wasn't significant "whether the two of them saw Dumbo or not."
Leverett, in his closing, said the charges against Fontan were important because Fontan's secrecy about his relationship with Elizabeth Sanchez put him and other cops in danger.
On Twitter: @julieshawphilly